army - fm90-13 - river crossing operations

Field Manual 90-13 *FM 90-13Marine Corps Warfighting Publication 3-17.1 MCWP 3-17.1

HeadquartersDepartment of the Army

Commandant, US Marine CorpsWashington, DC, 26 January 1998

River-Crossing Operations

TABLE OF CONTENTS

PagePreface......................................................................................................................................... vi

Chapter 1. Concepts ................................................................................................................ 1-1

General.................................................................................................................................. 1-1Types of Crossings ............................................................................................................... 1-1

Hasty................................................................................................................................. 1-1Deliberate ........................................................................................................................ 1-3Retrograde ....................................................................................................................... 1-4

Crossing Fundamentals ....................................................................................................... 1-4Surprise ........................................................................................................................... 1-4Extensive Preparation ..................................................................................................... 1-4Flexible Plan.....................................................................................................................1-5Traffic Control .................................................................................................................. 1-5Organization.....................................................................................................................1-5Speed................................................................................................................................. 1-6

Chapter 2. Terrain and Enemy .............................................................................................. 2-1

General.................................................................................................................................. 2-1Estimate of the Situation................................................................................................. 2-1Tactical Requirements ..................................................................................................... 2-1

Terrain .................................................................................................................................. 2-1Characteristics ................................................................................................................. 2-1Military Aspects ............................................................................................................... 2-2

DISTRIBUTION RESTRICTION: Approved for public release; distribution is unlimited. *This publication supersedes FM 90-13, 30 September 1992.

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PageCurrent ............................................................................................................................. 2-2Water Measurements....................................................................................................... 2-2Water Changes................................................................................................................. 2-3Obstructions ..................................................................................................................... 2-3The Friendly Shore .......................................................................................................... 2-4The Enemy Shore............................................................................................................. 2-4

Intelligence ........................................................................................................................... 2-5Priority Intelligence Requirements (PIR)....................................................................... 2-6Information Collection ..................................................................................................... 2-6

Threat ................................................................................................................................... 2-6River Defense ................................................................................................................... 2-6Offensive River Crossing ................................................................................................. 2-8

Chapter 3. Command and Control ......................................................................................... 3-1

General ................................................................................................................................. 3-1Organization ......................................................................................................................... 3-1Control Elements.................................................................................................................. 3-1

Division Headquarters..................................................................................................... 3-1Brigade Headquarters ..................................................................................................... 3-3

Communications................................................................................................................... 3-5Control Measures ................................................................................................................. 3-5

Release Lines (RLs).......................................................................................................... 3-5Crossing Areas ................................................................................................................. 3-5Waiting Areas................................................................................................................... 3-5Engineer Equipment Parks (EEPs) .............................................................................. 3-10Traffic-Control Posts...................................................................................................... 3-10Engineer Regulating Points .......................................................................................... 3-10

Crossing Plan ..................................................................................................................... 3-10Crossing Control................................................................................................................. 3-11

Assault Across the River................................................................................................ 3-11Crossing-Area Operations ............................................................................................. 3-11Transfer of Support Forces to Division ......................................................................... 3-12

Movement Control.............................................................................................................. 3-14Retrograde Crossings ......................................................................................................... 3-14

Chapter 4. Planning ................................................................................................................ 4-1

General ................................................................................................................................. 4-1The Planning Process........................................................................................................... 4-1

Analyzing the Mission ..................................................................................................... 4-2Developing COAs ............................................................................................................. 4-4Analyzing COAs ............................................................................................................... 4-5Comparing COAs ............................................................................................................. 4-5Producing Orders ............................................................................................................. 4-6

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PageChapter 5. Division Deliberate River Crossing .....................................................................5-1

General..................................................................................................................................5-1Phases of a Deliberate River Crossing ................................................................................5-1The River Crossing ...............................................................................................................5-1

Advance to the River (Phase I) ........................................................................................5-4Assault Across the River (Phase II) ................................................................................5-6Advance From the Exit Bank (Phase III) .......................................................................5-8Secure the Bridgehead Line (Phase IV) ..........................................................................5-9Continuation of the Attack ............................................................................................5-11

Chapter 6. Retrograde Operations .........................................................................................6-1

General..................................................................................................................................6-1Retrograde Types..................................................................................................................6-1

Delay .................................................................................................................................6-1Withdrawal .......................................................................................................................6-6Retirement........................................................................................................................6-6

Denial Measures ...................................................................................................................6-6Planning............................................................................................................................... 6-7

Chapter 7. Crossing Sites........................................................................................................7-1

General..................................................................................................................................7-1Crossing-Site Selection.........................................................................................................7-1Planning................................................................................................................................7-2Requirements........................................................................................................................7-2

Entry/Exit Routes or Paths .............................................................................................7-2Routes and Approaches....................................................................................................7-3Waiting Areas...................................................................................................................7-3River Conditions...............................................................................................................7-4Banks ................................................................................................................................7-4Bottoms.............................................................................................................................7-4Enemy Situation...............................................................................................................7-4

Site Analysis .........................................................................................................................7-4Field Calculations.................................................................................................................7-5

Measuring the Current’s Velocity ...................................................................................7-5Determining Slopes and Degrees ....................................................................................7-6Measuring the River's Width...........................................................................................7-7Calculating Downstream Drift ........................................................................................7-7

Rafts ......................................................................................................................................7-9Site Preparation ...............................................................................................................7-9Rafting Sites .....................................................................................................................7-9Rafting Operations .........................................................................................................7-12Maintenance and Refueling...........................................................................................7-13

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PageBridges ................................................................................................................................ 7-13

Site Organization ........................................................................................................... 7-14Night Operations............................................................................................................ 7-15Actions Under Fire......................................................................................................... 7-15Vehicle Recovery ............................................................................................................ 7-16

Other Gap-Crossing Equipment........................................................................................ 7-16

Chapter 8. Assault Crossing ................................................................................................... 8-1

General ................................................................................................................................. 8-1Types of Assault Crossings .................................................................................................. 8-1

Rubber-Boat Crossing...................................................................................................... 8-2Air-Assault Crossing........................................................................................................ 8-2Vehicle-Swim Crossing .................................................................................................... 8-3

Organization ......................................................................................................................... 8-3Support Force ................................................................................................................... 8-3Assault Force.................................................................................................................... 8-4Engineers.......................................................................................................................... 8-7

Preparation Phase of the Operation.................................................................................... 8-7Far-Shore Reconnaissance .............................................................................................. 8-7Far-Shore Preparation..................................................................................................... 8-8Nearshore Reconnaissance ............................................................................................ 8-10Assault-Force Rehearsal................................................................................................ 8-10

Execution Phase of the Operation ..................................................................................... 8-11Attack-Position Procedures ........................................................................................... 8-11Embarking Procedures .................................................................................................. 8-12Tactical Control Afloat................................................................................................... 8-13Watermanship................................................................................................................ 8-14Obscuring With Smoke .................................................................................................. 8-16Direct-Fire Reaction....................................................................................................... 8-17Indirect-Fire Reaction.................................................................................................... 8-17Debarking Procedures ................................................................................................... 8-17Boat Return .................................................................................................................... 8-17Motor Procedures ........................................................................................................... 8-18Cargo Procedures ........................................................................................................... 8-19Casualty Procedures ...................................................................................................... 8-19

Safety .................................................................................................................................. 8-20

Chapter 9. Engineer Operations ............................................................................................ 9-1

General ................................................................................................................................. 9-1ERP Operations.................................................................................................................... 9-1

Rafting Operations........................................................................................................... 9-2Bridging Operations......................................................................................................... 9-3Swimming Operations ..................................................................................................... 9-4

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PageEngineer Contingency Bridging Operations ....................................................................... 9-4

Assault Bridges, Long-Term Use .................................................................................... 9-5Maintenance .....................................................................................................................9-5Anchorage .........................................................................................................................9-5Protective Systems ...........................................................................................................9-6Approaches .......................................................................................................................9-7Long-Term Gap-Crossing C2............................................................................................9-8

Multirole Bridge Company (MRBC) ................................................................................... 9-8Organization.....................................................................................................................9-9Basic Concept ...................................................................................................................9-9Implications ....................................................................................................................9-10Training ..........................................................................................................................9-10

Appendix A. Metric Conversion Chart .................................................................................. A-1

Appendix B. Engineer-Planning Calculations ...................................................................... B-1

General................................................................................................................................. B-1Engineer Planning............................................................................................................... B-1

Appendix C. Crossing Means ................................................................................................. C-1

General................................................................................................................................. C-1Descriptions of Crossing Means.......................................................................................... C-1

Fording Vehicles.............................................................................................................. C-2Amphibious Vehicles ....................................................................................................... C-2Aircraft............................................................................................................................. C-2Boats ................................................................................................................................ C-2Assault Launched Bridges .............................................................................................. C-2Rafts ................................................................................................................................. C-2Bridges ............................................................................................................................. C-3

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PREFACE

Field Manual (FM) 90-13 describes how divisions and brigades conduct river crossings. Itshows the relationship to corps operations, where appropriate, and includes details for lowerechelons to support the brigades. It provides doctrine, tactics, techniques, and procedures(TTP) in one reference to accomplish this special operation.

The corps assigns missions and provides the necessary support and equipment. The divi-sions normally assign bridgehead objectives and control movement across the river. The bri-gades are the bridgehead forces that execute the crossings, either independently or aselements of a larger force.

River-crossing skills and knowledge are highly perishable. As with many other tactical oper-ations, they require constant practice in planning and execution. There are relatively fewopportunities to train with the frequency needed to keep a high degree of proficiency in thistough operation. For that reason, this manual includes considerable detail on techniquesand procedures.

A river crossing is a special operation in that it requires specific procedures for successbecause the water obstacle prevents normal ground maneuver. It demands more detailedplanning and technical support than normal tactical operations. It also features specific con-trol measures to move the force across a water obstacle. This obstacle may be a river, a lake,or a canal. Unlike other obstacle types, the water obstacle remains effective during and afterthe crossing operation. See FM 90-13-1 for other counterobstacle operations.

As in the past, the United States (US) Army conducts river crossings within the context ofits basic doctrine. This manual applies the current Army-operations doctrine described inFM 100-5 to river crossings. It incorporates recent developments in command and control(C2) for command-post (CP) facilities and the military decision-making process. It also alignsUS doctrine more closely with ongoing standardization efforts in the North Atlantic TreatyOrganization (NATO).

Appendix A contains an English to metric measurement conversion chart.

The proponent of this publication is HQ TRADOC. Send comments and recommendations onDepartment of the Army (DA) Form 2028 directly to Commander, US Army Engineer School,ATTN: ATSE-TD-D-WC, Fort Leonard Wood, MO 65473-6650.

This publication implements the following international agreement: Standardization Agree-ment (STANAG) 2395, Edition 1, Opposed Water Crossing Procedures.

Unless this publication states otherwise, masculine nouns and pronouns do not refer exclu-sively to men.

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CHAPTER 1

ConceptsGENERAL

The purpose of any river crossing is to projectcombat power across a water obstacle toaccomplish a mission. A river crossing is aunique operation. It requires specific proce-dures for success because the water obstacleprevents normal ground maneuver. It alsorequires detailed planning and control mea-sures and different technical support thanother tactical operations require. The natureand size of the obstacle, the enemy situation,and available crossing assets limit the tacti-cal commander's options.

The challenge is to minimize the river'simpact on the commander's ability tomaneuver. The force is vulnerable while

crossing, as it must break its movementformations, concentrate at crossing points,and reform on the far shore before continu-ing to maneuver. The tactical commandercannot effectively fight his force while it issplit by a river. He must reduce this vul-nerability by decreasing his force's expo-sure time. The best method is to crossrivers in stride as a continuation of the tac-tical operation, whether in the offense orretrograde. Only as a last resort shouldthe force pause to build up combat poweror crossing means before crossing. Thischapter introduces river-crossing opera-tions by discussing the characteristics ofthis special, difficult, and dangerous task.

TYPES OF CROSSINGSUnits expected to conduct a river crossinganticipate and plan for it in advance. Allriver crossings require detailed planning.The planning requirements and engineertechnical support are similar, whether thecrossing is hasty, deliberate, or retrograde.

HASTY

A hasty river crossing is a continuation ofan attack across the river with no inten-tional pause at the water to prepare, so thatthere is no loss of momentum. This is possi-ble when enemy resistance is weak and theriver is not a severe obstacle.

A hasty river crossing is preferable to adeliberate crossing. A hasty river crossingfeatures decentralized control at the bri-gade level. The brigade may use organic,existing, or expedient crossing means, butadditional support from the division orcorps is often necessary due to the bridge

companies being controlled at corps level.That support is only available when thoseheadquarters have taken purposeful actionto position the assets at the right time andplace to make a brigade hasty crossing fea-sible. Coordination for support must bemade early in the planning process.

Small gaps that prohibit vehicles from self-bridging are encountered more frequentlythan large gaps that require extensivebridging. Each maneuver force shouldtask-organize itself with organic mobilecrossing assets that enable it to installbridges quickly, cross small gaps, andrecover the bridges for future crossings.Follow-on bridges, such as the medium-girder bridge (MGB), may need to be posi-tioned before assault bridges are removedat these minor gaps. The two types ofhasty crossings are the dry- and wet-gapcrossings.

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Hasty Dry-Gap Crossing

Antitank (AT) ditches and craters are nor-mally what maneuver forces encounter as adry-gap-crossing obstacle. Dry riverbedsmay also present a crossing problem.Maneuver forces can use the M9 armoredcombat earthmover (ACE) to push down thesides of ditches or to fill in craters. Substan-tial fill material placed in the dry gapsallows the passage of combat tracked vehi-cles. The crossing site can be improved andmaintained for wheeled-traffic use by fol-low-on forces.

The armored vehicle-launched bridge (AVLB)is particularly suited for spanning stream-beds, AT ditches, craters, canals, partiallyblown bridges, and similar obstacles. It canbe launched and recovered in less than 5minutes. The AVLB, like the M9 ACE, isorganic to combat engineer companies for usein hasty crossings of short gaps. The AVLBshould be left in place across the gap only aslong as it takes to cross the maneuver unit itis traveling with, then replaced with otherfixed bridging, if necessary.

Hasty Wet-Gap Crossing

The depth and width of the wet gap, bankconditions, and the current’s velocity willdetermine if the maneuver force can crossby fording, swimming, or employing theAVLB or if other bridging assets arerequired. Identifying wet gaps early anddeploying the required resources allowhasty crossings of known or anticipatedgaps to occur. Two factors should be consid-ered when swimming vehicles through wetgaps—the current’s velocity and the bankconditions.

Because vehicles drain rapidly when exit-ing, initially firm banks tend to deterioraterapidly from multiple uses of the same exitpoint. The existence of mud or surface irreg-ularities further degrades the percent of the

slope that the swimming vehicle can over-come. When selecting a fording site in awet-gap crossing, the depth of the water isthe most significant factor. The depth of thewater in one crossing area may change dueto bottom surface mud or irregularities(boulders or pot holes). The AVLB is ideallysuited to allow hasty wet-gap crossings,requiring only that the supported maneuverforce eliminate enemy direct and observedindirect fires. The crossing means will needto be replaced by other bridging assets assoon as possible to allow the AVLB toremain with its supported unit.

If possible, the force crosses the waterobstacle at multiple points across a broadfront. It makes the crossing as soon as itselements reach the obstacle, whether by dayor night. As the bulk of the force crosses thewater, minimum forces remain to secure thecrossing sites.

Expedient crossing means may be used ifreadily available and can be transported tothe crossing site. The reconnaissance partyshould note material or existing featuresthat could be used as expedient crossingdevices. These include culvert pipe, lumberor cut timber, or war-damaged equipment.The pipe fascines system (PFS), which con-sists of bundles of 8-inch, high-density, plas-tic pipes chained together, can fill gaps up to9 meters deep and support up to 70 tons.The PFS is transported by an AVLB afterthe bridge is downloaded and emplaced intothe gap.

A well-practiced standing operating proce-dure (SOP) reduces the necessary planningand preparation time. A concise order,clearly articulating the commander'sintent, allows exploitation wherever subor-dinate units successfully force a crossing.When possible, advance elements seizeexisting crossing means intact and ahead ofthe main body.

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When facing negligible or light enemy resis-tance on both banks, the force does not haveto clear all enemy forces from the river toconduct a hasty crossing. It capitalizes onthe speed of the crossing and the limitedability of the enemy to effectively oppose thecrossing.

DELIBERATE

A deliberate river crossing is conductedwhen—

• A hasty crossing is not feasible.

• A hasty crossing has failed.

Opposition from a strong defending enemycan require a deliberate crossing. A deliber-ate river crossing is an attack across theriver after a halt to make the detailed prep-arations necessary to ensure success. It ischaracterized by—

• A significant water obstacle.

• Strong enemy resistance.

• The necessity to clear entry and/or exitbanks of enemy forces.

A deliberate river crossing involves the fol-lowing:

• Centralized division planning and control.

• Thorough preparations, to include thetime to perform extensive reconnais-sance and full-scale rehearsals, developalternate traffic routes, and stockpilelogistics.

• The massing of forces and crossingequipment.

The deliberate river-crossing organization isas follows:

• An assault force that seizes the far-shoreobjective and eliminates direct fire onthe crossing site.

• A maneuver-support force that consistsof corps combat engineers, bridge com-panies, military police (MP), and chemi-cal units which provide crossing means,traffic control, and obscuration.

• A bridgehead force that attacks from thefar-shore objective to secure the bridge-head, eliminating direct fire andobserved indirect fire on the crossingarea.

Once the river crossing is complete (bridge-head line is secured), a breakout forcecrosses the river behind the bridgeheadforce and attacks out of the bridgehead.This force is normally not a part of the unitthat conducted the river crossing.

The two types of deliberate crossings arewet- and dry-gap crossings.

Deliberate Wet-Gap Crossing

The deliberate wet-gap crossing is dividedinto the following three phases: assault,rafting, and bridging. These phases mayoccur in sequence or concurrently. Theobjective in deliberate wet-gap crossings isto project combat power to the exit bank ata faster rate than the enemy can concen-trate forces for a counterattack. To do this,the commander may elect to first constructrafts for nonswimming vehicles while swim-ming the fighting vehicles across. Bridgeconstruction is started when observed indi-rect fire has been eliminated. If the tacticalsituation allows the elimination of the raft-ing phase, bridging efforts should beginimmediately. This may be a suitable optionconsidering the high speed of employingsystems like the ribbon bridge.

Deliberate Dry-Gap Crossing

Deliberate dry-gap crossings are generallydetermined by the strength of the enemy'sdefenses or the magnitude of the gap. Ifpossible, using the M9 ACE or the AVLB is

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preferred. The MGB, the Bailey bridge,the M4T6 dry-span bridge and, in the nearfuture, the heavy dry-support bridge(HDSB) are used to span larger dry gaps.These assets are labor-intensive andexpose personnel to enemy fire during con-struction but provide stable gap-crossingsupport for continuous operations.

RETROGRADE

A retrograde river crossing is a movementto the rear across a water obstacle while in

contact with the enemy. The forces con-ducting the crossing establish a defense onthe exit bank or continue the retrograde tothe defensive positions beyond the waterobstacle. A retrograde river crossing fea-tures centralized planning and controlbecause of the limited crossing means. Ithas the same amount of detailed planningas for a deliberate offensive crossing. Fail-ure of a retrograde crossing may lead tolosing a significant amount of friendlyforces.

CROSSING FUNDAMENTALSRiver-crossing fundamentals are the samefor all river crossings, but their applicationvaries. For example, traffic control is a keyfundamental. The commander maintains itin a hasty crossing by using the unit’s SOPand a fragmentary order (FRAGO). In adeliberate crossing, he uses a traffic-controlorganization, such as the MP, that imple-ments a detailed movement plan. Crossingfundamentals must be applied to ensuresuccess when conducting a river crossing.These fundamentals include—

• Surprise.

• Extensive preparation.

• Flexible plan.

• Traffic control.

• Organization.

• Speed.

SURPRISE

The range and lethality of modern weaponsallow even a small force to defeat a largerexposed force caught in an unfavorable posi-tion. A river provides this possibility by—

• Limiting a force to a small number ofcrossing sites.

• Splitting the force’s combat power onseparate banks.

• Exposing the force to fires while on thewater.

Surprise minimizes these disadvantages;forces that fail to achieve surprise may alsofail in the crossing attempt.

A deception plan is a key element of sur-prise. It reinforces the enemy's predisposi-tion to believe that the force will take aparticular course of action (COA). Theenemy usually expects a crossing; however,it does not know where or when. A deceptionplan that employs reconnaissance, site prep-arations, force buildup, and preparatoryfires at a time or location other than theintended crossing area may delay an effec-tive enemy response to the true crossing.

The usual operations security (OPSEC) mea-sures are also important. Commandersenforce camouflage, noise, thermal, electro-magnetic, and light discipline. In particular,commanders closely control movement andconcealment of river-crossing equipment andother obvious river-crossing preparations.Despite modern intelligence-gatheringtechnology, the skillful use of night, smoke,fog, and bad weather for obscuration is stilleffective.

EXTENSIVE PREPARATION

Comprehensive intelligence of the enemy’scomposition and disposition and crossing-area

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terrain must be developed early, since plan-ning depends on an accurate and completeintelligence picture.

Supporting forces, which typically includeengineer battalions, bridge companies, air-defense batteries, smoke-generation compa-nies, and MP companies, must link up early.They immediately begin crossing prepara-tions and are available to train the crossingforce during rehearsals.

Commanders plan and initiate deceptiveoperations early to mask the actual prepa-ration. These operations should concealboth the time and location of the crossing,so they begin before and continue through-out the preparation period.

Work necessary to improve routes to handlethe traffic volume of the crossing operationshould occur early enough not to interferewith other uses of the routes. This requiresa detailed traffic plan carefully synchro-nized with the deception plan.

Full-scale rehearsals are essential to clarifyroles and procedures, train personnel,inspect equipment, develop teamwork, andensure the unity of effort.

FLEXIBLE PLAN

Even successful crossings seldom go accord-ing to plan. A flexible plan enables thecrossing force to adapt rapidly to changes inthe situation during execution. It allows theforce to salvage the loss of a crossing site orto exploit a sudden opportunity. A flexibleplan for a river crossing is the result of thor-ough staff planning, not chance. Such a planfeatures—

• Multiple approach routes from assemblyareas (AAs) to crossing sites.

• Lateral routes to redirect units to alter-nate crossing sites.

• Alternate crossing sites and stagingareas to activate if enemy action closesthe primaries.

• Crossing equipment held in reserve toreplace losses or open alternate sites.

TRAFFIC CONTROL

A river is a significant obstacle that slowsand stops units, thus impeding their abilityto maneuver. Units are restricted to movingin column formations along a few routesthat come together at the crossing sites.Traffic control is essential to cross units atthe locations and in the sequence desired.Maximum crossing efficiency is achievedthrough traffic control. It also prevents theformation of targets that are susceptible todestruction by artillery or air strikes. Inaddition, effective traffic control contrib-utes to the flexibility of the plan byenabling commanders to change thesequence, timing, or site of crossing units.The traffic-control organization can switchunits over different routes or hold them inwaiting areas as directed by the tacticalcommander.

ORGANIZATION

Commanders use the same C2 nodes forriver crossings as they do for other opera-tions. These nodes, however, take on addi-tional functions in river crossings. For thisreason, commanders specify which nodesand staff positions have specific river-crossing planning and control duties. Thismay require some temporary collocation ofheadquarters cells (or individual augmenta-tion) and an increase in communicationsmeans.

The tactical commander organizes his unitsinto assault, maneuver-support, and bridge-head forces. He organizes support forcesconsisting of engineer, MP, and chemicalunits, as well as other combat-support

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units, into a crossing organization. Thisorganization reports to the tactical com-mander’s controlling headquarters. Sincethis is a temporary grouping, proceduresthat the controlling headquarters estab-lishes must be clear, simple, and rehearsedby all elements to ensure responsive sup-port of the plan and the unity of command.

Terrain management is an integral part ofthe crossing operation. The controllingheadquarters assigns space for supportforces to work on and for assault forces toconcentrate on before crossing. Otherwise,they interfere with each other and become

lucrative targets for indirect fires andenemy air attacks.

SPEEDA river crossing is a race between the cross-ing force and the enemy to mass combatpower on the far shore. The longer the forcetakes to cross, the less likely it will succeed,as the enemy will defeat, in detail, the ele-ments split by the river. Speed is so impor-tant to crossing success that extraordinarymeasures are justified to maintain it. Thecommander must allow no interferencewith the flow of vehicles and units once thecrossing has started.

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CHAPTER 2

Terrain and EnemyGENERAL

Commanders maneuver their forces intopositions of advantage over the enemy.Engineers analyze the terrain to determinethe maneuver potential, ways to reduce nat-ural and enemy obstacles, and how theycan deny freedom of maneuver to theenemy by enhancing the inherent obstaclevalue of the terrain.

ESTIMATE OF THE SITUATION

Commanders and staffs develop estimatesof the situation, described in FM 101-5, dur-ing the military decision-making process.Terrain and enemy aspects that are applica-ble to estimates for river-crossing opera-tions are discussed in this chapter. Much ofthis information directly applies to theintelligence preparation of the battlefield(IPB). Refer to FM 34-130 for more informa-tion on the IPB process.

TACTICAL REQUIREMENTSAlthough terrain characteristics have astrong influence, tactical requirements ulti-mately determine the location of the cross-ing site(s). River conditions must allow theemployment of available crossing meansand the tactics required for the operation.

The far-shore terrain must support missionaccomplishment; otherwise, crossing theriver there serves little purpose. Crossingsites must also support the rapid movementof units to the far shore, or the enemy canwin the force buildup race. Commandersbalance the tactical use of the far-shore ter-rain against technical crossing require-ments at the river to determine suitablecrossing locations.

Nearshore terrain must support initialassault sites, rafting and bridging sites,and the assembly and staging areas usedby the force. Routes to and from the rivermust support the quantity of traffic that isnecessary for the operation and for the sus-tainment of the force in subsequent opera-tions.

The enemy’s disposition of forces may limitoptions for the commander. Because theriver physically splits his force, he shouldexecute his crossing operation where theenemy is most vulnerable or least able toreact. This gives the commander time tomass his force on the far shore before theenemy can concentrate against it.

TERRAINThe engineer is the terrain expert. He mustwork closely with the Intelligence Officer(US Army) (S2) during the planning pro-cess to determine advantages and disadvan-tages the terrain gives to both friendly andenemy forces.

CHARACTERISTICS

Rivers form unique obstacles. They are gen-erally linear and extensive and normally

cannot be bypassed. Meandering bends inrivers provide far-shore defenders withopportunities for flanking fires and observa-tion of multiple crossing sites. Thecombined-arms team, as normally config-ured for combat, needs special preparationand equipment to carry it across river obsta-cles. After the attacking force crosses theriver, it remains an obstacle for all follow-onforces.

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A formation cannot breach a river wher-ever desired, as it can with most fieldobstacles. Likely crossing sites can be fewand equally obvious to both the attackerand defender.

A river provides excellent observation andfields of fire to both the attacker anddefender. It exposes the force on the waterand makes it vulnerable while enteringand leaving the water. It is also an aerialavenue of approach, allowing enemy air-craft low-level access to crossing opera-tions.

Force buildup on the far shore is a racebetween the defender and the attacker.The river can be an obstacle behind the ini-tial assault force, allowing the enemy topin and defeat it in detail while preventingrapid reinforcement.

MILITARY ASPECTS

Terrain analysis for a river crossingincludes the following military aspects ofterrain: observation, cover and concealment,obstacles, key terrain, and avenues ofapproach (OCOKA). However, many detailsare peculiar to river crossings. These detailsinclude the specific technical characteris-tics of the river as an obstacle.

CURRENT

The current of a river is a major limitingfactor. It imposes limits on all floatingequipment, whether rubber assault boats,swimming armored vehicles, rafts, orbridges. The current’s velocity determinesthe amount of personnel/equipment eachtype of floating equipment can carry or if itcan operate at all. Current affects the dis-tance that the floating equipment will driftdownstream. Therefore, commanders musteither select an offset starting pointupstream to reach a desired point on thefar shore or take additional time to fightthe current. High current velocities make

control of a heavy raft difficult; therefore,landings require skilled boat operators andraft commanders and more time.

Current causes water pressure againstfloating bridges. Bridge companies useboats or an anchorage system to resist thispressure. The higher the current the moreextensive the anchorage system must be.Higher currents provide velocity to floatingobjects, which can damage or swamp float-ing equipment.

Current can be measured easily (for exam-ple, by timing a floating stick) but is nor-mally not constant across the width of theriver. Generally, it is faster in the centerthan along the shore. It is also faster on theoutside of a curve than on the inside. A fac-tor of 1.5 times the measured currentshould be used for planning purposes.

WATER MEASUREMENTS

The depth of the water influences allphases of a river crossing. If the water isshallow enough and the riverbed will sup-port traffic, fording is possible. If the forceuses assault boats and the water becomesshallow in the assault area, the force willhave to wade and carry their equipment.Shallow water also causes difficulty forswimming vehicles, as the rapidly movingtracks can dig into a shallow bottom andground the vehicle. The water must bedeep enough to float bridge boats andloaded rafts on their crossing centerlinesand deep enough in launch areas to launchboats and bridge bays. The depth of thewater is not constant across a river. It isgenerally deeper in the center and in high-velocity areas. Either a bottom reconnais-sance with divers or sounding from areconnaissance boat is necessary to verifythe depth.

The width of a river is a critical dimensionfor bridges (especially, when it determines

2-2 Terrain and Enemy

FM 90-13/MCWP 3-17.1

how much equipment is necessary) and forrafts. The distance a raft must travel deter-mines its round-trip crossing time, which inturn determines the force buildup rate onthe far shore.

WATER CHANGES

A swell is the wave motion found in largebodies of water and near the mouths of riv-ers. It is caused by normal wave action in alarger body, from tidal action, or from windforces across the water. A swell is a seriousconsideration for swimming armored vehi-cles and is less important for assault boats,heavy rafts, and bridges. Hydrographic dataand local residents are sources of informa-tion on swells. Direct observation has lim-ited use, as a swell changes over time withchanging tide and weather conditions.

Tidal variation can cause significant prob-lems. The depth and current of waterchange with the tide and may allow opera-tions only during certain times. Tidal varia-tion is not the same every day, as it dependson lunar and solar positions and on the cur-rent's velocity. Planners need tide tables todetermine the actual variation, but they arenot always available for rivers. Anothertidal phenomenon found in some estuariesis the tidal bore, which is a dangerous wavethat surges up the river as the tide enters.It seriously affects water operations. Thisreverse flow may require that float bridgesbe anchored on both sides.

Rivers may be subject to sudden floods dueto heavy rain or thawing upstream. Thiswill cause bank overflow, higher currents,deeper water, and significant floatingdebris. If the enemy possesses upstreamflood-control structures or dams, it cancause these conditions also.

OBSTRUCTIONS

Most rivers contain sand or mud banks.They are characteristic of low-current areas

along the shore and on the inside of thecurves of a river, but they can be anywhere.Since they cause problems for swimmingvehicles, assault boats, outboard motors,bridge boats, and rafts, troops must findthem through underwater reconnaissanceor sounding.

Rocks damage propellers, boats, and float-ing bridges and ground rafts. They causeswimming armored vehicles to swamp if thevehicle body or a track rides up on themhigh enough to cant the vehicle and allowwater into a hatch or engine intake. Theycan also cause a fording vehicle to throw atrack. Rocks are found by underwater recon-naissance or sounding.

Natural underwater obstructions and float-ing debris can range from sunken ships towreckage and snags. The current in largewaterways can carry significant floatingdebris, which can seriously damage boatsand floating equipment. Usually, debris canbe observed after flooding or rapidly risingwaters. Underwater reconnaissance orbottom-charting sonar is the only way tolocate underwater obstructions.

Man-made underwater obstacles can be steelor concrete tetrahedrons or dragon's teeth,wood piles, or mines. The enemy places themto deny a crossing area and designs them toblock or destroy boats and rafts. Underwaterreconnaissance or bottom-charting sonar canlocate these obstacles.

Vegetation in the water can snag or chokepropellers and ducted impellers on outboardmotors and bridge boats. Normally, floatingvegetation is not a significant problem.Thick vegetation beds that can cause equip-ment problems are found in shallow waterand normally along the shore. As thick veg-etation must extend to within 30 to 60 centi-meters of the surface to hinder equipment,it can normally be seen from the surface.


FM 90-13/MCWP 3-17.1

THE FRIENDLY SHORE

Concealment is critical to the initial assaultacross the river. The assault force musthave concealed access to the river. It mustalso have concealed attack positions close tothe river from which to prepare assaultboats. The overwatching unit prepares con-cealed positions along the friendly shore,taking full advantage of vegetation and sur-face contours. Overwatching units must bein position to engage the most likely enemyposition(s) on the enemy shore.

Dominant terrain formed by hill masses orriver bluffs provides direct-fire overwatchpositions. If the dominant terrain is alongthe shore, it also covers attack positions,AAs, and staging areas. Air-defense (AD)sites should be located on terrain that domi-nates aerial avenues of approach (one ofwhich is located along the river). Whenselecting a crossing site, consider the follow-ing:

• Dismounted avenues of approach thatallow silent and concealed movement ofassault battalions to the river.

• Concealed attack positions that are veryclose to the water along the dismountedavenue.

• Approaches from the attack positions tothe water that have gradual slopes andlimited vegetation to allow the assaultforce to carry inflated assault boats.

• Bank conditions that are favorable. Dis-mounted forces must be able to carryassault boats to the water, and engineertroops must be able to construct and oper-ate rafts with little bank preparation.

• Road networks that feed the crossingsites and support the lateral movementof vehicles between sites. These road net-works must be well constructed to carrylarge amounts of heavy vehicle traffic.

• Potential staging areas that can supportlarge numbers of tracked and wheeledvehicles without continual maintenance.

• Helicopter landing zones (LZs) forembarkation of the assault force.

THE ENEMY SHORE

River meanders form salients and reentrantangles along the shore. A salient on theenemy shore is desirable for the crossingarea, as it allows friendly fires from a widestretch of the near shore to concentrateagainst a small area on the far shore andlimits the length of enemy shore that mustbe cleared to eliminate direct fire and obser-vation (see Figure 2-1).

Dominant terrain is undesirable on theenemy shore. Any terrain that permitsdirect or observed indirect fires onto cross-ing sites is key terrain. Friendly forces mustcontrol it before beginning the rafting orbridging phases.

Natural obstacles must be minimal betweenthe river and the bridgehead objectives.River valleys often have parallel canals, rail-road embankments, flood-control structures,swamps, and ridges that can impede morethan the river itself. Obstacles perpendicularto the river can help isolate the bridgehead.

Exits from the river must be reasonably goodwithout preparation. Initially, the bankshould allow the assault force to land and dis-mount from the assault boats. This requiresshallow banks with limited vegetation. Theassault force also requires concealed dis-mounted avenues up from the river. Bankconditions must allow vehicles to debarkfrom rafts and move up from the river. Ifbanks require earthwork, at least one unim-proved crossing site must allow the landingof earthmoving equipment. The most impor-tant far-shore requirement is a road networkto carry high volumes of heavy vehicle traffic.


FM 90-13/MCWP 3-17.1

Reentrant

Salient

Rive

r Enemy shoreFriendly shore

2-1

Figure 2-1. Salient and reentrant on the enemy shore

INTELLIGENCEDetailed knowledge of the river and adjacentterrain is critical to both tactical planningand to engineer technical planning. The keysare early identification of intelligencerequirements and an effective collection plan.Space-based imaging and weather systemscan provide invaluable information to the ter-rain database. Multispectral imagery (MSI)from satellites can give the engineer terraindetachment a bird's-eye view of the area ofoperations. Satellite images, the largest 185by 185 kilometers, can be used to identify keyterrain and provide crossing locations. Theseimages can provide information concerningthe depth and turbidity of the river and canbe used to identify the line of site for weaponsand communications systems. With MSIproducts, prospective construction materials,the locations of existing crossing sites, andnearshore and far-shore road networks canbe identified and exploited.

When the MSI is combined with satelliteweather receivers, data processors, and theterrain database, it can be used to identifymobility corridors and establish floodplaintrafficability. When these space systems areused together, the effects of the weather on

terrain can be analyzed and used to developdecision-support products for the com-mander.

The terrain database is the starting pointfor obtaining terrain information. Hydro-graphic studies exist for most rivers inpotential theaters of operation around theworld. Many of these studies have sufficientdetail for identifying feasible crossing sites.Modern information-collection and -storagetechnology permits frequent revision ofexisting data.

Engineer terrain detachments at corps anddivision maintain the terrain database andprovide information in the form of topo-graphic products. These products are usedwith other tools, such as computers and pho-tography, to develop terrain intelligence forstaff planners. The planners, in turn, deter-mine initial crossing requirements and esti-mated crossing rates from their terrainanalyses.

Early in the mission analysis, planners iden-tify further terrain-intelligence needs for thecrossing. They provide this to the Assistant


FM 90-13/MCWP 3-17.1

Chief of Staff, G2 (Intelligence) (G2) for inclu-sion in the intelligence-collection plan. Theplan specifies that intelligence systems areused to gather essential terrain informationfor a more detailed analysis. Information onspecific river segments and the surroundingterrain is obtained and verified by aerial andground reconnaissance.

PRIORITY INTELLIGENCEREQUIREMENTS (PIR)

The following tactical and technical infor-mation is often PIR for executing a success-ful crossing:

• Enemy positions that can place direct orobserved indirect fires on crossing sitesand approaches.

• The location and type of enemy obsta-cles, particularly mines, in the waterand on exit banks.

• The location of enemy reserves that cancounterattack assault units.

• The location of enemy artillery that canrange crossing sites, staging areas, andapproaches.

• The location and condition of existingcrossing sites.

• The width, depth, and velocity of the river.

• The condition and profile of the river’sbottom.

• The height, slope, and stability of thebank.

• The condition of nearshore and far-shoreroad networks.

• Previous enemy tactics for defendingwater obstacles.

• Floodplain trafficability.

INFORMATION COLLECTION

Engineer units have the primary responsi-bility to collect the terrain informationneeded for river crossings. If the river isunder friendly control, engineer units col-lect river, bank, and route information. Ifit is not, space- (satellite) or computer-based intelligence should be accessed, ormaneuver units with attached engineerreconnaissance teams should conductreconnaissance operations to obtainneeded information. Engineer light divingteams obtain far-shore, nearshore, river-bottom, and underwater-obstacle informa-tion. Local inhabitants provide additionalinformation about bridges, the flow of ariver and the stability of its banks, roadnetworks, ford sites, and other river condi-tions. Aviation assets can provide aerialand video reconnaissance to greatlyenhance the IPB for river-crossing opera-tions. Normal intelligence-collection assetsdevelop the picture of the enemy’s defensethat is necessary for templating.

THREATLeaders who understand enemy tacticscan defeat the enemy at the river for a suc-cessful crossing. Many potential enemiesuse doctrine from the former Soviet Union,making their tactics the most likely onesUS forces must overcome during a cross-ing. Therefore, the discussion in the follow-ing paragraphs describes an opposing-force (OPFOR)-style defense and an attackat a river as the most likely threat. See US

Army Training and Doctrine Command(TRADOC) Pamphlet 350-14 for details onan OPFOR defense and TRADOC Pam-phlet 350-16 for OPFOR water crossings.

RIVER DEFENSE

The threat considers a water obstacle to bea natural barrier, enabling a strong defenseon a wide front with small forces. Unitsmust be prepared to conduct operations in a


FM 90-13/MCWP 3-17.1

high level of mission-oriented protectiveposture (MOPP). The threat prefers todefend on a riverbank that is under its com-plete control. It can, however, defend for-ward or to the rear of a river. Its choicedepends on the terrain, the forces availableto it, and their strengths. The threat consid-ers the defensive characteristics of the ter-rain. It weighs the severity of the obstacle,the effect of lost crossing sites, and the pos-sibility of severed supply lines.

The threat may defend forward when theterrain is favorable, when it has sufficientreserve combat power, or when it plans toresume the offense immediately. Whendefending forward, it intends to defeat thecrossing force before it reaches the river.The threat will place its defensive forces asfar forward of the river as possible.

First-echelon regiments of a division in themain defensive belt forward of a river estab-lish initial defensive positions 10 to 15 kilo-meters from the river. Second-echelonregiments occupy positions within a fewkilometers of the river. These positions areastride major avenues of approach to blockattacking forces so that a counterattack candestroy them.

When defending along a river, the threatplaces most of its forces as close to the exitbank as defensible terrain permits. Theirmission is to protect the crossing sites anddefeat the crossing force while it is dividedby the river. The arrangement of defensivebelts is similar to the defense forward of theriver, except that the distance between first-and second-echelon regiments may be less.This concentrates more force to defeatassault forces on the exit bank.

Threat engineers destroy existing bridgesand mine known crossing sites. They keeponly a few sites open for the withdrawal ofthe predominantly amphibious security

force. Threat engineers also emplace obsta-cles along approach and exit routes, includ-ing the riverbanks. As time and assetspermit, they add obstacles such as floatingmines and underwater obstructions to fur-ther disrupt crossing efforts.

First-echelon defensive forces maneuver tobring maximum defensive fire on the cross-ing force. These defensive forces engage thecrossing force with all possible organic andsupport weapons at crossing sites while it iscrossing. Their mission is to defeat the cross-ing force before it can establish a bridgehead.

Second-echelon battalions, astride majoregress routes from the river, block assaultelements so counterattacking forces canengage and destroy battalion or smallerassault elements. Second-echelon regi-ments occupy positions 4 to 5 kilometersbehind the first echelon. They provide depthto the defense. It is from this area that thethreat launches local counterattacks.

The threat undertakes a defense to the rearof a river when time or terrain precludes adefense forward of the river or on the exitbank. In this situation, security elementsdeploy on the exit bank to harass and dis-rupt the attacker's assault and supportforces. These security elements delay theattacker to provide time to establish themain defense.

A significant threat capability against ariver crossing is artillery. Therefore, if theS2 indicates that the threat has formedartillery groups (regimental artillery groups[RAGs], division artillery groups [DAGs], orArmy artillery groups [AAGs]), then it hasthe capability to saturate crossing sites. Inthis case, it is not sufficient to eliminate thethreat’s observation of the river beforebuilding bridges, as the concentration ofartillery fires can deny an entire bridgingsite without the necessity for observed fires.


FM 90-13/MCWP 3-17.1

The threat can also place rafting operationsat risk, as it can place artillery fires on theentrance bank, the exit bank, and the raftcenterline simultaneously. Therefore, thisrequires counterbattery fire to be plannedand coordinated to counter threat artilleryattacks on the crossing sites.

OFFENSIVE RIVER CROSSING

The threat's offensive river-crossing capabil-ity has a significant effect on retrogradecrossings by US forces. Threat doctrineespouses direct and parallel pursuit. Thethreat's ability to force a crossing on a flankand cut off friendly elements before they cancomplete the retrograde crossing is a majorconcern.

The threat is well prepared to cross waterobstacles. On the average, it anticipates thata formation on the offense will cross onewater obstacle of average width (100 to 250meters) and several narrower ones each day.It considers the crossing of water obstacles tobe a complex combat mission but regards thisas a normal part of a day's advance.

The threat has two assault-crossing meth-ods. The first one is an assault crossingfrom the line of march. This it does on themove, having prepared its subunits for thecrossing before they approach the waterobstacle. The other method is the preparedassault crossing—the main forces deploy atthe water obstacle and cross after makingadditional preparations. The success of thethreat's crossings is determined by the fol-lowing:

• Careful preparation.

• Reconnaissance of opposing forces andthe water obstacle.

• Surprise.

• Air superiority.

• Destruction of opposing forces by fire.

• Timely advance of crossing resources.

• Personnel and equipment control at thecrossings.

• Strict compliance with safety measures.

Threat doctrine calls for relentless pursuitto prevent the opponent from disengaging,to seize available crossing sites quickly, andto cross the obstacle on the heels of with-drawing forces. Forward detachments andadvanced guards have a large role in this.A forward detachment reaches the waterobstacle as quickly as possible, bypassingstrongpoints, and captures existing bridgesor river sections suitable for an assaultcrossing. It crosses the water, seizes key ter-rain on the opposite bank, and holds it untilthe main force arrives.

The threat achieves protection from itsopponent along routes to the river by usingconcealing terrain and creating verticalscreens out of vegetation and metallic cam-ouflage nets. Once the crossing begins, thethreat uses smoke and thermal decoys todefeat precision-guided munitions.

Threat tactical doctrine recognizes thattime is a decisive factor in the success ofan assault crossing from the line of march.The threat anticipates that it should takea forward detachment (battalion) 1 to 1 1/2hours, a first-echelon regiment 2 to 3hours, and a division 5 to 6 hours to crossa river of moderate width (100 to 250meters).

When an assault crossing from the line ofmarch is not feasible, the threat uses theprepared assault crossing. Here, the mainforce deploys at the water obstacle with sub-units in direct contact with the opponent.The threat then makes more thorough prep-aration for the crossing. Success dependson covertness, so the crossing usually takesplace at night.


FM 90-13/MCWP 3-17.1

CHAPTER 3

Command and ControlGENERAL

Unity of effort is established by the C2

emplaced on the maneuver units, the crossing-force headquarters, and the supportingunits. Unit organization and traffic controlare fundamental to successful river-crossingoperations. They enable the commander to

apply the tactics discussed in Chapters 5and 6. This chapter covers the techniquesand procedures used to establish the cross-ing organization, maintain control of forces,and hand off responsibilities between eche-lons as the operation progresses.

ORGANIZATIONDivision and brigade commanders orga-nize their forces into assault, maneuver-support, bridgehead, and breakout forcesfor river-crossing operations. Assaultforces seize the far-shore objective to elimi-nate direct fire on the crossing sites.Maneuver-support forces consist of corps

combat engineers, bridge companies, MP,and chemical units that provide crossingmeans, traffic control, and obscuration.Bridgehead forces secure the bridgehead.Breakout forces cross the river behind thebridgehead forces and attack out of thebridgehead.

CONTROL ELEMENTSDivision and brigade commanders areresponsible for crossing their formations.They organize their staffs and subordinatecommanders to help them control the cross-ing (see Table 3-1, page 3-2). Division and bri-gade headquarters operate from echelonedCPs. They are the tactical, main, and rearCPs and provide the staff and communica-tions support for planning and executingriver crossings. The CPs may need some tem-porary augmentation or realignment of inter-nal staff elements for the crossing. Figures 3-1 and 3-2, pages 3-3 and 3-4, show the neces-sary control elements for deliberate and ret-rograde river-crossing operations. Each of thecontrol elements is discussed below.

DIVISION HEADQUARTERS

The division tactical CP (DTAC) controls thelead brigades' (bridgehead force) attackacross the river, since this is the division'sclose fight. It may reallocate crossing means

or movement routes to the river betweenbrigades as the battle develops. The DTACis the crossing-force headquarters.

The division main CP (DMAIN) preparesthe river-crossing plan. It also directs thedivision's deep operations to isolate thebridgehead from enemy reinforcements andcounterattacking formations. As a guide,the DMAIN displaces across the river afterthe division reserve. For division crossings,a traffic-control cell schedules, routes, andmonitors traffic behind the lead brigades.The cell collocates with the DMAIN. TheAssistant Chief of Staff, G4 (Logistics) (G4)provides the cell nucleus.

The division rear CP (DREAR) sustains thecrossing for other division operations. Oncethe DMAIN displaces across the river, thecrossing becomes a rear operation that theDREAR controls.

Command and Control 3-1

FM 90-13/MCWP 3-17.1

Crossing-Force Commander (CFC)

The division commander normally desig-nates an assistant division commander(ADC) as the CFC to take charge of control-ling the division crossing.

Crossing-Force Engineer (CFE)

A crossing division receives support from aCFE, who is normally the commander of anengineer group from the corps engineer bri-gade. He provides additional staff planners

Phases

CPs

Advance to the River

Assault Across the

River

Advance From the Exit Bank

Secure the Bridgehead

Line

Continue the Attack

DTAC (crossing force’s headquarters)

Coordinates the lead brigade’s seizure of nearshore objectives

Coordinates the lead brigade’s dismounted assault of the river to seize the far-shore objectives

Coordinates the lead brigade’s seizure of exit-bank and intermediate objectives

Coordinates the lead brigade’s seizure and securing of bridgehead objectives and prepares to cross the reserve brigade (breakout forces)

Controls the breakout force’s attack out of the bridgehead and passes the crossing force’s responsibilities to the DREAR

DMAIN Coordinates deep operations to isolate the division’s advance to the river

Coordinates deep operations to isolate the crossing area and the far-shore objectives

Coordinates deep operations to isolate exit-bank and intermediate objectives

Coordinates deep operations to isolate the bridgehead

Coordinates deep operations to isolate the enemy’s attack against corps objectives

DREAR Sustains the fight

Sustains the fight

Sustains the fight

Sustains the fight

Assumes the role of the crossing force’s headquarters

BTAC Coordinates the lead TF’s seizure and securing of nearshore objectives

Coordinates the dismounted assault crossing of the river to secure the far-shore objectives

Coordinates the TF’s attack to seize and secure exit-bank and intermediate objectives

Coordinates the TF’s seizure and securing of bridgehead objectives

Prepares to reorganize and follow the breakout force’s attack out of the bridgehead toward the division’s deep objectives

BMAIN (crossing-area headquarters)

Moves into the crossing area to provide traffic control, crossing means, and obscuration

Coordinates assault crossing means for TFs dismounted and controls obscuration of the crossing sites

Controls follow-on TFs passing through the crossing area into attack positions

Controls the passage of the brigade’s units through the crossing area and prepares to cross breakout forces

Passes crossing-area control to the supporting corps’s engineer battalion

Table 3-1. CP tasks (deliberate crossing)

3-2 Command and Control

FM 90-13/MCWP 3-17.1

for the CFC and coordinates engineer sup-port to the crossing-area commanders(CACs).

BRIGADE HEADQUARTERS

Each brigade headquarters operates fromecheloned CPs, the brigade tactical CP(BTAC), and the brigade main CP(BMAIN). The BTAC controls the advanceto and the attack across the river. It dis-places across the river as soon as practicalafter the assault across the river to control

the fight for exit-bank, intermediate, andbridgehead objectives.

The BMAIN controls the crossing of therest of the brigade. It prepares the brigadecrossing plan and provides the staffnucleus to coordinate it. For brigade cross-ings, the Supply Officer (US Army) (S4),assisted by the supporting MP unit leaderor engineers if available, organizes asmall, temporary traffic-control cell collo-cated with the BMAIN.

CA C

CA E

x

RB

xMai n

RB

xxxxx

R LR L

Br i d g eh ea dl i ne

CF C

xxT AC

CF Exxx

Cr os s i ng a re a

X

CS C

CS C

X

X

T AC

XX

Figure 3-1. Control elements for a deliberate crossing (brigade focus)

Crossing area

Bridge-headline

RB

RB

MainCAC


FM 90-13/MCWP 3-17.1

CSC

CAC

CAE CSC

x

RB

TAC

xMain

RB

xxx xx

RL RL Holdingline

CFC

xxTAC

CFExxx

CB T

Crossing area

XX

X

X

X

Figure 3-2. Control elements for a retrograde crossing (brigade focus)

Crossing-Area Commander

Once the lead battalions assault across theriver and secure the far-shore objective,the crossing area is activated. The CAC,normally the brigade's executive officer(XO), controls the movement of forcesinside the crossing area. The BMAIN con-trols the maneuver-support force that con-sists of corps engineers, bridge companies,and MP and chemical units. This leavesthe brigade commander free to direct keyactivities while an officer who is directlyresponsible to him runs the crossing. TheCAC controls—

• The movement and positioning of allelements transiting or occupying posi-tions within the crossing area.

• Security elements at crossing sites.

• Maneuver-support forces, such as engi-neer, MP, and chemical units within thecrossing area.

Crossing-Area Engineer (CAE)

Each forward brigade will normally be sup-ported by a direct-support engineer battalionfrom the corps. The engineer battalion com-mander is responsible to the CAC for the


FM 90-13/MCWP 3-17.1

engineer crossing means and sites. Heinforms the CAC of changes, due to technicaldifficulties or enemy action, that render acrossing means inoperable or reduce itscapacity. He commands those engineerstasked to move the force across the river;they remain there as the attack proceedsbeyond the exit-bank objectives. The divisionengineer battalion focuses on supporting thelead brigades at exit-bank, intermediate, andbridgehead objectives and is not normallyinvolved in the river crossing.

Crossing-Site Commander (CSC)

Each crossing site has an engineer, either acompany commander or a platoon leader,who is responsible for crossing the unitssent to the site. Normally, the CSC is thecompany commander for the bridge unit

operating the site. He commands the engi-neers operating the crossing means and theengineer regulating points (ERPs) at thecall-forward areas for that site. He main-tains the site and decides on the immediateaction needed to remove broken-down ordamaged vehicles that interfere with activi-ties at the site. He is responsible to the CAEand keeps him informed on the status of thesite.

Unit-Movement-Control Officer

Each battalion and separate unit com-mander designates a movement-controlofficer, who coordinates the unit's move-ment according to the movement-controlplan. He provides staff planners withdetailed information on the unit's vehicletypes and numbers.

COMMUNICATIONSFigures 3-3 and 3-4, pages 3-6 and 3-7,depict the communications networks withina crossing area. In the hasty-crossing exam-ple, a brigade making a supporting attackconducts a crossing with its normal slice ofcombat-support forces plus a corps bridgecompany. More assets are available from the

division and corps in the deliberate-crossingexample. Wire is the preferred means ofcommunications in a river crossing whenthere is sufficient time to prepare it. Thecorps engineer battalion will establish wirecommunications with the nearshore cross-ing area according to the crossing plan.

CONTROL MEASURESThe commander uses control measures todelineate areas of responsibility for subor-dinates and to ease traffic control. Figure3-5, page 3-8, illustrates the control mea-sures described below.

RELEASE LINES (RLS)

As used in river-crossing operations, RLsare used to delineate the crossing area. RLsare located on both the far and near shoresand indicate a change in the headquartersthat is controlling movement. RLs are nor-mally located within 3 to 4 kilometers ofthe river and on easily identifiable terrainfeatures, if possible.

CROSSING AREAS

Crossing areas are controlled access areasthat decrease congestion at the river. Thispermits swift movement of forces. Each leadbrigade has a crossing area on both sides ofthe river that is defined by brigade bound-aries and RLs. Crossing areas normallyextend 3 to 4 kilometers on each side of theriver, depending on the terrain and theanticipated battle.

WAITING AREAS

Waiting areas are located adjacent to theroutes or axes of advance. Commandersuse the following waiting areas to conceal


FM 90-13/MCWP 3-17.1


1 TCP

2

TCP

TCP

3

AA

R B

E E P

Call-forwardareas

M P

C F E

Crossingsites

xx

x x x

X

X X

X X X

XX X(-)

x

Main body

Maneuver-supportforces

Holdingareas

Staging areas

River

Holdingareas

Assaultforces

M P

Figure 3-3. Communications for a deliberate crossing

EEP

Main

Main

TAC

...

...

...

...

CAE

CFE

FM 90-13/MCWP 3-17.1


1 TCP

2

TCP

TCP

3

R B

E E P

Call-forwardareas

M P

C F E

C A E

Crossingsites

xx

x x x

X

X X

X X X

XX X(-)

x

Main body

Maneuver-supportforces

Holdingareas

Staging areas

River

Holdingareas

Assaultforces

M P

Figure 3-4. Communications for a hasty crossing

EEP

TAC

Main

Main

...

...

...

CFE

...

MP

CAE

FM 90-13/MCWP 3-17.1


RP

4RP

Staging area Green 31

RL Apple

(Engineertraffic only)

Call-forward areaGreen 33

Holding areaGreen 32

To site Green 1

Call-forwardareaGreen 21

NOTE: Arrowsparallel to roadsshow the directionof trafficmovement.

RL Pear

Attack positionGreen 34

Site Green 2(swim)

Holdingarea

Site Green 3(raft)

River

EEPGreen 35

River

2

RL Pear

RL Apple

Alt

(Engineer traffic only)

Alt

3

2-3 km

2-3 km

Crossing areaGreen

6

1 1

6

7

8

9

3

2

CenterlineEast

1

Figure 3-5. Control measures

TCP

TCP

ERP

ERP

TCP

TCP

TCP

TCP

TCP

TCP

TCP

ERP

ERP

CenterlineMiddleCenterline

West

(Engineer traffic only)

FM 90-13/MCWP 3-17.1

vehicles, troops, and equipment while wait-ing to resume movement or to make finalcrossing preparations:

• Staging areas.

• Call-forward areas.

• Holding areas.

• Attack positions.

• AAs.

Staging areas

Staging areas are battalion-size waitingareas outside the crossing area where forceswait to enter the crossing area. The brigadetraffic-control cell handles units’ movementinto staging areas. The CAC controls move-ment from the staging areas into the cross-ing areas. MP operate traffic-control posts(TCPs) at staging areas according to thecrossing and traffic-circulation plans. Theyemplace temporary signs along the routefrom the staging area through the crossingarea to guide convoys. Units make crossingpreparations and receive briefings on vehi-cle speed and spacing in the staging areas.Staging areas—

• Are located to support the crossing con-cept.

• Are far enough back to permit thererouting of the battalion along otherroads or to alternate crossing sites.

• Are easily accessible from major routes.

• Have sufficient area for dispersing abattalion-size unit.

• Provide concealment.

Call-Forward Areas

Call-forward areas are company-size wait-ing areas located within the crossing area.Engineers use them to organize units intoraft loads, or crews use them to make finalvehicle swimming preparations. The CACcontrols movement from the staging area tothe call-forward area. The CSC directs

movement from the call-forward area to thecrossing site and on to the far-shore attackposition. As a minimum, each CSC operateshis own call-forward area. Call-forwardareas—

• Are located to support the crossing plan.

• Are company size within the crossingarea.

• Are easily accessible from routes.

• Are planned with a minimum of one percrossing site.

• Have ERPs collocated with them.

• Are used to organize units into raft loads.

• Are the final preparation areas beforegoing to the crossing site.

• Are normally operated by engineers.

Holding Areas

Holding areas are waiting areas that forcesuse during traffic interruptions. Units moveinto these areas when directed by TCP per-sonnel and disperse rather than stay on theroads. Holding areas are battalion size out-side of the crossing area and company sizewithin it. Far-shore holding areas are used toorganize return traffic. MP and engineers, ifavailable, operate holding areas according tothe crossing and traffic-circulation plans.Established as needed on both sides of theriver, holding areas—

• Are used as call-forward areas for returntraffic from the far shore.

• Are located to support the crossing plan.

• Are easily accessible from routes.

• Have sufficient area for dispersion.

• Provide cover and concealment.

• Are defensible.

• Maximize traffic flow with minimumcontrol.


FM 90-13/MCWP 3-17.1

Attack Positions

Attack positions are the last positions occu-pied or passed through by the assault eche-lon or attacking force before crossing theline of departure. Within the bridgehead,the attack position is the last positionbefore leaving the crossing area or bridge-head line.

Assembly Areas

AAs are areas in which a force prepares orregroups for further action.

ENGINEER EQUIPMENT PARKS (EEPS)

EEPs are areas located a convenient distancefrom bridging and rafting sites for assem-bling, preparing, and storing bridge equip-ment and material. They are at least 1kilometer from the river and hold spareequipment and empty bridge trucks that arenot required at the crossing sites. EEPsshould be located where they do not interferewith the traffic to the crossing sites andwhere equipment can be concealed and dis-persed. Ideally, routes leading from EEPs tothe crossing sites are not the same routesused by units crossing the river.

TRAFFIC-CONTROL POSTS

In river crossings, TCP personnel assistthe crossing-area headquarters in trafficcontrol by reporting and regulating the

movement of units and convoys. TCP per-sonnel relay messages between the cross-ing-area headquarters and moving units.The provost marshal identifies locationsthat need or require TCPs. MP or engi-neers, if available, operate TCPs on bothbanks of the river to control traffic movingtoward or away from it. TCPs are addition-ally operated at major or critical crossroadsand road junctions, staging areas, holdingareas, and ERPs.

ENGINEER REGULATING POINTS

ERPs are technical checkpoints which areused to ensure that vehicles do not exceedthe capacity of the crossing means. Theyhelp maintain traffic flow. Vehicles whichwill not be allowed to cross are removed sothat they do not cause a traffic backup atthe actual crossing site. Engineers man theERPs and report to the CSC. TCPs are collo-cated with the ERPs to ensure that all vehi-cles clear the call-forward areas. Anadditional duty of ERP personnel is to givethe drivers final instructions on site-specificprocedures and other information such asspeed and vehicle intervals. As a minimum,each crossing site requires an ERP at itsown call-forward area. If sufficient engineerassets are available, ERPs may be estab-lished at far-shore holding areas to regulaterearward traffic.

CROSSING PLANThe crossing plan is integrated throughoutthe division's and brigade's operationorders (OPORDs) and is as detailed as timepermits. The crossing annex to the OPORDcontains much but not all of the plan. It hasthe crossing overlay and the crossing syn-chronization matrix.

The crossing overlay shows the crossingareas, the crossing sites, the routes leadingup to them from waiting areas, and all thecontrol measures necessary for the crossing

(see Figure 3-6). The crossing synchroniza-tion matrix is a tool to adjust the crossingplan as the battle develops. It shows cross-ing units in relation to their planned cross-ing times and locations. See Appendix B foran example matrix.

The task organization paragraph and para-graph 5 of the OPORD contain the organiza-tion and command portions of the crossingplan. For more information on the develop-ment of the crossing plan, see Chapter 4.


FM 90-13/MCWP 3-17.1

1

3

42

CBT

CAC

x

Mai nCAE

1

501

HoldingareaRed 33

1x3

1x3

HoldingareaRed 31

AA Maple

Holding area

Route 2Red 21

StagingareaRed 22

StagingareaRed 32

RL Grape

Call-forward area

Call-forward area

Site Red 4

Red 24

PLRiver RL Apple

Red 35

Site Red 3

RLApple

Site Red 1

Attackposition

Red 21

541D xx23AD

Attackposition

Red 25

1x3

541D xx23AD

541D xx23AD

Site Red 2

E R P

E R P

5

6 7

8 3

1

RL Grape

E R P

Crossing area Red

4

Figure 3-6. Crossing overlay

Red 23

Route 3

TCP

Holding area

TCP

TCP10

Holding area

TCP

TCP TCPTCP

ERPERP

ERP

ERP

TCP TCPTCP

CROSSING CONTROLCommanders use control measures to oper-ate, delegate authority, and lead from anycritical point during the river-crossing oper-ation while synchronizing other criticalactions throughout their area of operations.

ASSAULT ACROSS THE RIVERBattalion task forces (TFs) conducting theassault across the river move to it under thedirect control of their brigade commanders.The assault TFs using rubber boats 15(RB15s) follow the procedures in Chapter 8.The brigade commander keeps the remain-der of the brigade back from the river toavoid congestion. Elements not engaged in

security or supporting the crossing occupyAAs and prepare for movement across theriver.

CROSSING-AREA OPERATIONS

After the assault across the river, the brigadehas an initial position on the far shore and isno longer fighting to seize the exit bank. Thebrigade needs its follow-on forces across asquickly as possible. The battalions can nowcross without engaging in combat at theriver. The brigade commander activates thecrossing area to move forces rapidly and effi-ciently. The urgent need to get tanks acrossthe river means the rafting stage often


FM 90-13/MCWP 3-17.1

begins before terrain on the far shore issecure to the planned RL. Therefore, thecrossing area is initially limited to the nearshore. The first fighting vehicles swimmingor rafting across under this circumstancehave limited space to regroup before commit-ment to the fight.

As the initial battalions cross, they gain ter-rain to the necessary depth, and as controlelements cross to the far shore, the brigadecommander extends the crossing area out tothe planned RL. Thereafter, units move com-pletely through the crossing area under theCAC's control and exit it in a tactical move.

When rafting, the crossing flow for the fol-low-on units is generally from a stagingarea, through the call-forward area andcrossing site into an attack position, andthen on to a subsequent objective. Whilebridging, the flow is from a staging area,through the crossing site, and then out ofthe crossing area.

Figure 3-7 illustrates the traffic flow for a fol-low-on battalion TF during the rafting. Thisprocedure avoids congestion close to the cross-ing site and helps maintain unit integritywhile the battalion rafts. The battalion occu-pies staging area Green 31 and organizes aninternal unit crossing order based on its mis-sion on the far shore. When concurrentlyswimming and rafting vehicles of the samebattalion, the swimming vehicles form up sep-arate from nonswimming vehicles for move-ment to the crossing sites and reform into atactical formation at the far-shore attack posi-tion. ERP personnel at the call-forward areacheck to determine the correct load classifica-tion and proper loading sequence for eachvehicle. When instructed by the CAC, thebattalion sends one company at a time (or theequivalent) from the staging area. TCP per-sonnel guide the company's movement enroute to a call-forward area where it comesunder the movement control of the CSC.

In the call-forward area at site Green 33,ERP personnel organize individual vehiclesinto raft loads. They guide the raft loadsdown to the raft centerlines as the CSCdirects. In the call-forward area at site Green21, vehicle crews make the final vehicleswimming preparations. ERP personnel sendthe vehicles down to the swimming site whendirected by the CSC.

Vehicles remain under the control of theCSC until they are on the far shore. Therethey proceed to attack position 6, wherethey regroup as a company/team. Whenready, the TF commander, under the tacti-cal control of the brigade commander, con-trols the movement of the vehicles.

During bridging operations, the CAC nor-mally directs the follow-on battalions tomove in company serials from the stagingarea. Each serial moves down to the bridgesite, crosses the river, and continues on tothe attack position. The CAC directs aninterval between serials that keeps contin-uous traffic across the bridge without gapsor traffic jams. A call-forward arearemains established in the event that thebridge becomes damaged and units mustbe held until raft operations resume.

Units in the support-by-fire position onthe near shore are already inside the cross-ing area when the crossing operationstarts. They remain in this position untilthe CAC directs them to cross the river,and then they move directly to previouslyselected call-forward areas or start points(SPs) by company or platoon.

TRANSFER OF SUPPORT FORCES TO DIVISION

Once the bridgehead forces are across theriver, the crossing sites are relativelysecure. Since ground maneuver is no longerclose to the crossing area, the operation atthe river becomes predominantly a bridging


FM 90-13/MCWP 3-17.1


Figure 3-7. Follow-on-TF crossing during a rafting phase

TCP

RP

Staging area Green 31

RL Apple

Call-forward areaGreen 33

Holding areaGreen 32

Call-forwardareaGreen 21

NOTE: Arrows parallel to roadsshow the direction of trafficmovement.

RL Pear

Attackposition6

Site Green 2(swim)

Holdingarea

Site Green 3(raft)

RiverRiver

RL Pear

RL Apple

4

3

1 1

3

2

6

ERP

4

5

2

ERP

ERP

TCP

TCP

TCP

TCP

TCP

TCP

FM 90-13/MCWP 3-17.1

and traffic-scheduling problem. The divisionheadquarters moves the RL at the rear ofthe bridgehead force to the far shore. Thecrossing areas come under direct divisioncontrol. As the ADC directs, the brigadecommander turns over his crossing area to

another officer, normally the CAE, whobecomes responsible for the crossing area.The CAE then reports through the CFE tothe ADC at the DREAR. The CAE's unitheadquarters becomes the crossing-areaheadquarters.

MOVEMENT CONTROLMovement control is vital to efficiently moveunits and material up to the crossing areain the sequence needed by the commander.The traffic-control cells at the division andbrigade headquarters exercise movementcontrol through TCPs. The division controlsmovement from its rear boundary up to thebrigade rear, and the brigade controls move-ment from the rear boundary up to thebridgehead line.

The division transportation officer (DTO)develops the division movement planaccording to the movement priorities that

the Assistant Chief of Staff, G3 (Operationsand Plans) (G3) and the G4 establish. TheS4 prepares the brigade movement planaccording to the priorities that the Opera-tions and Training Officer (US Army) (S3)establishes. Each unit-movement officer,normally the battalion S4, provides theunit's vehicle information to the planningheadquarters.

The movement plan normally consists of atraffic-circulation overlay and a road-movementtable found in the movement annex to thedivision's or brigade's order.

RETROGRADE CROSSINGSA retrograde river crossing has most of thesame control features as an offensive cross-ing. The commander responsible for acrossing area has the same authority as hedoes in an offensive crossing. When a bri-gade establishes a defense along the riverconcurrent with the crossing, the com-mander coordinates crossing activities toavoid conflicts with defensive prepara-tions. For this reason, the responsibleofficer and his staff should be familiarwith both the delaying and defending com-manders' tactical plans. He coordinatesoptimum use of crossing sites by delayingforces. As the delaying forces disengage,they must rapidly pass through the defend-ing force and cross the river. The com-mander responsible for the crossing areareports to the division CP controlling theoperation. If the main CP is forward of theriver, C2 is usually at the DREAR until themain CP displaces behind the river.

When the river is in the division’s rear areaat the start of the retrograde, the crossingbegins as a rear operation. The senior corpsengineer commander supporting the divi-sion becomes the CFE and establishes divi-sion crossing areas with corps engineer andMP units. He identifies engineer command-ers, as directed by the commanding gen-eral, to quickly organize the crossing areasand initiate crossing control. These cross-ing areas correspond to the brigade bound-aries planned by the G3 for the defensealong the river.

Each brigade commander establishing adefense at the river appoints an XO to con-trol the crossing area in his sector. Whenthe river is in the brigade's sector at thestart of the retrograde, this officer canimmediately take charge and organize thecrossing area. If the division initially orga-nizes the crossing area through the CFE,


FM 90-13/MCWP 3-17.1

it directs the defending brigade to takecharge of the crossing area once it hasestablished its hasty defense at the river.Then the engineer who was responsible forthe crossing area becomes the CAE. Thebrigade XO coordinates with the DMAIN,which retains centralized control of thecrossing until only the defending brigade'sunits remain to cross in that area. Thecrossing area is used until the commanderdirects the bridges to be destroyed orremoved. At that time, the crossing areaceases to exist.

Turnover of the sites from the CAC to thedefending battalion commanders is by

mutual agreement or when directed by thebrigade commander. Simultaneous handoffbetween or within defensive sectors is notessential. Depending on the tactical situa-tion, the division commander may notallow crossing equipment to remain inplace, even though the defending brigadecommander desires its retention. Nor-mally, the CAC retains control of the cross-ing means until delaying forces cross theriver. He then orders the removal of thetactical bridging assets. Control of theremaining fixed bridges then passes to thedefending commanders. They are responsi-ble for their defense and ultimate destruc-tion, as discussed in Chapter 6.


FM 90-13/MCWP 3-17.1

CHAPTER 4

PlanningGENERAL

Units plan river crossings the same as anytactical operation, with one major differ-ence. Force allocation against enemy unitshas an added dimension of time. Friendlyforces can only arrive on the battlefield atthe rate at which they can be broughtacross the river. This rate changes at differ-ent times throughout the operation. Thischapter outlines the detailed planning nec-essary because of this difference.

The corps allocates support elements to thedivision and provides terrain and enemyanalyses. It assigns mission objectives tothe division. For operations where the corpsis crossing the river, it may assign thebridgehead line.

The division assigns mission objectives tothe brigades and specifies the bridgeheadline. It may assign bridgehead objectives tothe brigades. The division allocates maneu-ver and maneuver-support forces to the bri-gades and develops coordination measures,such as movement schedules, that apply tomore than one brigade. The division alsoprovides terrain and enemy analyses to thebrigades.

The senior corps engineer headquarters,allocated to the division for the crossing,

assists the division engineer section withdetailed crossing plans. The lead brigadedevelops the tactical plans that it will exe-cute. It develops the crossing objectives inorder to attain its mission objective.

The headquarters of the corps engineerbattalion, assigned to support each bri-gade crossing, develops the detailed cross-ing plan. The battalions develop thetactical plan necessary to seize assignedobjectives.

The actual planning process for a rivercrossing is the same as for any tactical oper-ation. Differences occur primarily becauseof the complexity of crossing a river (whichmakes extensive calculation necessary) andthe need to balance tactics with crossingrates.

Planners do crossing calculations twice.Crossing calculations are critical to COAevaluation. They are required to ensurethat force buildup supports the COA. Forinitial planning, simple calculations andrules of thumb are used to produce quickforce-buildup information. Once a com-mander selects a specific COA, plannersmake detailed crossing calculations to pro-duce the crossing plan.

THE PLANNING PROCESSThe staff planning process produces a bestpossible solution to accomplish the unit'smission. This chapter discusses those partsof planning that are necessary for a rivercrossing. It does not attempt to discuss thelarger planning process necessary for fullmission accomplishment.

In the following paragraphs, the planningprocess is described in steps and by eche-lons. The shadowed text in the tables showsthe step in the planning process being dis-cussed, with the battle staff and engi-neer planning requirements alongside. Adetailed discussion that is primarily aimed

Planning 4-1

FM 90-13/MCWP 3-17.1

at the division and brigade echelons follows.In general, the corps identifies the crossingrequirement and provides assets, the divi-sion conducts a detailed terrain analysisand develops rough crossing plans, and thebrigade develops detailed crossing plans.

ANALYZING THE MISSION

The first step is to recognize that a rivercrossing is necessary (see Table 4-1). Oncethe mission is received, the staff developsand conducts a mission analysis. This isdone to—

• Understand the purpose of the missionand the intent of the commander and thecommander two levels up.

• Review the area of operations.

• Identify tasks (both specified andimplied), assets available, constraints,restraints, and an acceptable level ofrisk.

A mission analysis is conducted according toFM 101-5. Corps planners normally identifyriver-crossing requirements when assigning

missions to the division. The corps plan willthen provide river-crossing assets to the divi-sion and may specify crossing the river as oneof the tasks assigned to the division. If themission the corps is assigning does notrequire a division-level river crossing, it maynot specify a crossing. The troop list includesnecessary crossing assets, however.

Normally, if the corps identifies the require-ment for a river crossing, its warning order(WO) includes it. The topographic companysupporting the corps provides detailed riverdata and crossing-area overlays. The topo-graphic company automatically providesnecessary topographic data to the divisionterrain team. See FM 100-15 for moredetails on planning at the corps level.

The division discovers that it must cross ariver by receiving a specified task in thecorps’s order or by developing an impliedtask during mission analysis. The divisionengineer’s section always examines all riv-ers in the division’s area of operations dur-ing the mission-analysis process. The

Table 6-1. Step 1 - receive the mission

Military Decision-Making Process

Actions to be Taken

Receive the mission The battle staff—

• Identifies critical facts and assumptions.

• Conducts an initial IPB by—- Identifying key terrain affecting the crossing.- Templating enemy river defenses.- Estimating the crossing capability of the area to be crossed,

using terrain data and available crossing means.- Calculating force crossing rates for each crossing area, using

the troop list.- Templating enemy obstacle systems.- Reviewing available bridging assets.

• Determines specified, implied, and essential tasks.

• Recognizes that a river-crossing operation is necessary.

• Issues a WO.

• Determines the CCIR as pertaining to the river crossing.

Analyze the mission

Develop COAs

Analyze COAs

Compare COAs

Approve a COA

Produce orders

Table 4-1. Step 2 - analyze the mission

4-2 Planning

FM 90-13/MCWP 3-17.1

division terrain team maintains a terraindatabase that includes river data andpotential crossing sites for the division’sarea of operation.

NOTE: Upon identifying a river-crossing task, the division engineerand terrain team immediately deter-mine potential crossing sites.

Intelligence Preparation of the Battlefield

The battle staff, including the staff engi-neer's help, analyze the existing situation.This analysis includes the enemy, friendlytroops, terrain, and time available for themission. This step is primarily designed toacquire the data necessary for the followingplanning steps, but some early analysis isnecessary to generate critical information.The engineer staff officer must very quicklyconvert raw terrain data and friendly infor-mation into crossing rates. This allows theplanners to make intelligent decisions aboutsupportable schemes of maneuver.

As a part of the IPB process, the G2 leadsthe staff development of a defensive situa-tional template along the entire river thatthe division must cross. The templatefocuses attention on possible areas of weak-ness, counterattack forces, and artillery.

The G2, with the division engineer’s help,develops obstacle templates from the line ofcontact through to division objectives. Heprovides the templates to the brigade intel-ligence sections for their planning and anal-ysis. The division engineer provides enemyobstacle information (particularly along theriver) to the brigade engineers.

The division provides the brigade staff withtemplates that it refines and further developsfor the enemy force in its area of operation.The S2 develops intelligence requirementsand a detailed intelligence-collection plan,with specific emphasis on the far shore.

Reconnaissance teams seek information tofill those requirements. Obstacle templatesare verified by active air and ground recon-naissance, as directed in Chapter 2.

Friendly Troops

The division engineer coordinates for corpsengineer units to cross the force, using thesimple rule of thumb that every forward bri-gade requires two bridges. Insufficientbridging assets limit possible COAs.

The brigade engineer identifies the crossingsites required for the brigade and for eachbattalion based on the number of vehicles.This calculation is based on simple assump-tions. From it, the brigade engineer deter-mines the approximate time necessary tocross the entire brigade (see Appendix B).The crossings required are important duringCOA development. The brigade engineer alsodetermines the amount of bridging available,the number of possible heavy rafts, and thenumber of assault boats. This information isforwarded to the CAE, who is responsible forthe control of all crossing means.

Terrain

The division engineer ensures that ade-quate information is in the crossing-sitedatabase for planning at brigade level. Thedivision terrain team generates crossing-site overlays, site data files, and road andcross-country-movement overlays for thecrossing areas.

The division engineer ensures that suffi-cient assault, raft, and bridge sites areavailable within each assault-brigade area.Generally, a main attack brigade requiresassault sites for two dismounted battalionsand at least two raft or bridge sites.

The brigade engineer, coordinating with theCAE, evaluates all potential crossing sitesfrom both technical and tactical consider-ations, including—

Planning 4-3

FM 90-13/MCWP 3-17.1

• Entry- and exit-road networks.

• Cross-country movement.

• The width, velocity, and depth of theriver.

• The conditions of the bank.

• The vegetation along the shore.

• The obstacles in or along the river.

• Possible attack positions and routes tothe river.

• Possible call-forward areas.

The brigade engineer, coordinating with theCAE, then analyzes each site to arrive at arough crossing-rate capability and theeffort necessary to open the site. Opera-tional planners use this information todevelop possible COAs.

The division engineer, coordinating with theCFC, ensures that the crossing require-ments of the lead brigades and breakoutforce are adequately resourced to satisfyeach COA.

The BMAIN evaluates the terrain along theriver in terms of OCOKA. The intent is tounderstand the terrain along the river so

that potential COAs can be devised withcrossing objectives. The operations plannerscombine this knowledge with the crossing-site comparisons and enemy templates todevelop possible COAs.

DEVELOPING COAs

The G3, along with key members of the bat-tle staff, sketches out possible COAs toaccomplish the mission of the division (seeTable 4-2). COAs must include—

• Assigned crossing areas for each bri-gade.

• Brigade boundaries that include terrainwhich is necessary to defend the bridge-head against enemy counterattacks.

Looking two levels down, the division staffplans an assault-crossing site for each antic-ipated assault battalion in a brigade’s area.A brigade should also have two bridging orrafting sites within its boundaries.

The S3 looks closely at the avenues leadingto brigade mission objectives, particularlyat crossing sites feeding the avenues.Developing practicable COAs is normallyan iterative process. The division staff firstdevelops a scheme of maneuver to take thefinal objective, then verifies that the force

4-4 Planning


Actions to be Taken

Receive the mission The battle staff—• Sketches out, with the commander’s assistance, several COAs to

develop.

• Develops the scheme of maneuver, fire plan, and support plan for each COA, considering crossing capability and the order of crossing.

The engineer selects sites, determines rafting and bridging configura-tions and bank-preparation requirements, and task-organizes the engineers for each COA.

Analyze the mission

Develop COAs

Analyze COAs

Compare COAs

Approve a COA

Produce orders

Table 4-2. Step 3 - develop COAs

FM 90-13/MCWP 3-17.1

build-up rate across the river is adequatefor the scheme of maneuver. If so, the S3expands the COAs to include the tacticsrequired for the crossing.

The tactics required for the crossing arebased on enemy defenses near the crossingsites, enemy reaction forces and earliestemployment times, and crossing rates ateach site. The COAs must include exit-bank,intermediate, and bridgehead objectives.

The S3, working with the brigade engineerand CAE, develops the control measures,crossing graphics, and crossing time line foreach COA (see Figure 4-1).

ANALYZING COAs

The staff at both the division and brigadewar-game each COA against likely enemyreactions (see Table 4-3, page 4-6). Theythen attempt to counter each enemyresponse.

The engineer—

• War-games against other variables out-side his control, such as terrain difficul-ties and crossing-equipment losses.

• Considers what will happen—

- If it takes longer to open a crossingsite.

- If damage slows progress overentrance and exit routes.

- If the conditions of the river change.

• Considers what will happen if enemyaction shuts down a crossing site orforces its relocation.

• Must consider the consequences of equip-ment failure or loss to enemy action.

• Evaluates the most likely of theseagainst all COAs and develops, withinhis means, necessary counters to includealternate sites and routes.

COMPARING COAs

The division staff examines each COAagainst both the immediate and follow-onmissions (see Table 4-4, page 4-6). The divi-sion is particularly concerned with themovement of reserve and support forces andcompares COAs against these requirements.

The brigade staff considers the ability ofeach COA to handle enemy responses, sup-port follow-on missions, provide brigadeflexibility, and allow for crossing redun-dancy.

Planning 4-5

Assault 1

Site 1

Site 2

Assault 2

Site 3

H-1 H+1 H+2 H+4H+3

TF 1-1

Prep TF 1-2

Prep TF 2-1

TF 2-2

H

Not used

Figure 4-1. Crossing time line

FM 90-13/MCWP 3-17.1


Actions to be Taken

Receive the mission The battle staff war-games each COA against possible enemy responses.

The engineer war-games each COA against terrain changes and equipment loss.

Analyze the mission

Develop COAs

Analyze COAs

Compare COAs

Approve a COA

Produce orders

Table 4-3. Step 4 - analyze COAs

PRODUCING ORDERSThe battle staff converts the selected COAinto a plan with sufficient detail for synchro-nized execution (see Table 4-5). The staffengineer conducts an extensive analysis todevelop a unit-by-unit crossing plan andmovement schedule in conjunction with theG3, G4, and DTO. From this analysis, hedevelops the crossing-capability chart (seeAppendix B) and the crossing overlay (seeFigure 3-6, page 3-11). These are his primaryexecution tools. The staff engineer develops

the crossing-synchronization matrix as a pri-mary execution tool for the S3 (see AppendixB). He also helps the traffic-control cell workout the traffic-circulation plan.

While detailed planning is underway, theCAE initiates far-shore and nearshorereconnaissance to develop sufficient detailfor battalion-level planning. He convertsthis planning into a detailed engineer tasklist and develops an engineer executionmatrix to synchronize it (see Appendix B).

Table 4-4. Step 5 - compare COAs

4-6 Planning

Military Decision-Making Process Actions to be Taken

Receive the mission The battle staff—

• Compares and evaluates the advantages and disadvantages of the COAs.

• Recommends one COA to the commander.

The commander selects a COA and issues a FRAGO.

Analyze the mission

Develop COAs

Analyze COAs

Compare COAs

Approve a COA

Produce orders

FM 90-13/MCWP 3-17.1

Table 4-5. Step 6 - produce orders


Actions to be Taken

Receive the mission The battle staff converts the selected COA into an executable plan.

The engineer develops a detailed crossing plan.Analyze the mission

Develop COAs

Analyze COAs

Compare COAs

Approve a COA

Produce orders

Planning 4-7

FM 90-13/MCWP 3-17.1

CHAPTER 5

Division Deliberate River CrossingGENERAL

A division deliberate river crossing is anoperation conducted as part of an offensiveoperation. The intent of a deliberate rivercrossing is to quickly cross a river and rap-idly secure the bridgehead line. It is meticu-lously planned and coordinated with allconcerned elements. A deliberate river cross-ing requires thorough reconnaissance andextensive evaluation of all intelligence. Itrequires detailed planning and preparation,centralized control, and extensive rehearsals.

A deliberate river crossing is costly in termsof manpower, equipment, and time. It is gen-erally conducted against a well-organizeddefense when a hasty river crossing is notpossible or when one has failed. A deliberateriver crossing requires the concentration ofcombat power on a narrow front, capitalizingon the element of surprise. The phases, eche-lons, organizations, and C2 of a division delib-erate river crossing are discussed in detail inthis chapter.

PHASES OF A DELIBERATE RIVER CROSSINGAn offensive deliberate river-crossing opera-tion has four phases. They are distinctphases for planning, but there is no pausebetween them in execution. The phases areas follows:

• Advance to the river (Phase I). The firstphase is the attack to seize the near-shore objective.

• Assault across the river (Phase II). Thesecond phase involves units assaultingacross the river to seize the far-shoreobjective, eliminating direct fire on thecrossing sites.

• Advance from the exit bank (Phase III).The third phase is the attack to secure

exit-bank and intermediate objectivesthat eliminate direct and observed indi-rect fires into the crossing area.

• Secure the bridgehead line (Phase IV).The final phase involves units thatsecure bridgehead objectives to protectthe bridgehead against a counterattack.This gains additional time and space forthe buildup of forces for the attack out ofthe bridgehead.

These phases are followed immediately byan attack out of the bridgehead by follow-on forces to defeat enemy forces at subse-quent or final objectives. Figure 5-1, page5-2, relates the crossing phases to theobjectives described in this chapter.

THE RIVER CROSSINGThe following section describes a deliberateriver-crossing operation from the division'sand brigade's perspectives. It details theactions that are required in deep, close, andrear operations by phase (see Figure 5-2,page 5-3).

A division is normally the smallest organi-zation that can conduct a deliberate river-crossing operation. It is usually an impliedtask in a larger mission given by the corps.The river crossing is not the objective butis part of the scheme of maneuver and

Division Deliberate River Crossing 5-1

FM 90-13/MCWP 3-17.1

overall offensive action against the enemy.The enemy will normally use the river as atactical obstacle system to slow and gainpositional advantage against the division'sadvance. The intent of the division is to

maintain its momentum through the cross-ing.

Mission, enemy, terrain, troops, and timeavailable (METT-T) dictate the force

Figure 5-1. Deliberate river crossing

Exit-bankobj

Bridge-headobj

Far-shoreobj

Intobj

Finalobj

Advance tothe river

Seize thenearshoreobjective

Advance from theexit bank

Secure exit-bank andintermediate objectivesto eliminate direct andindirect fires on thecrossing area

Sieze thefar-shore ob-jective, elimin-ating directfire on thecrossingsites(activate thecrossingarea)

Secure thebridgehead line

Seize and securebridgehead objectives toprotect the bridgeheadagainst counterattacksand create time andspace for the buildup offorces for the attack outof the bridgehead bybreakout forces; extendthe crossing area

Continue offensivecombat operations

Continue the attackon to the division'sand the corps'sobjectives

River-Crossing Phases

Phase I Phase III Phase IV

Crossingarea

Phase II

Assaultacross theriver

Phase

Assaultboats(begin constructing rafts)

Rafts(begin constructing float bridges)

Bridges

Mission

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allocation required during each phase of theoperation. Aside from the normal planning,detailed march tables are required for therapid passage of units through the crossingarea into the bridgehead. Detailed plans aredisseminated before the execution to ensurean uninterrupted operation. River-crossingoperations normally restrict movement tofour to six routes. This requires disciplinedand controlled movement to ensure thatcombat power builds in the bridgehead fasterthan the enemy's ability to react.

An integral part of the river-crossing opera-tion is the deception plan. The corps willplan, resource, and control all of the

requirements to execute a believable decep-tion so that the enemy does not know wherethe division will conduct the deliberateriver-crossing operation.

To conduct the deliberate river crossing, thedivision requires augmentation from thecorps. The corps must provide bridge compa-nies that are in direct support to the divisionfor the river-crossing operation in addition toother combat engineers that are required tooperate assault boats, provide C2, and soforth. An assault float bridge (AFB) companymust have an engineer group or ad hoc bat-talion staff that can support the deliberateriver-crossing operation and can remain in

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The BTACs control close operations to seize the nearshore, far-shore, exit-bank,intermediate, and bridgehead objectives.The BMAINs control smoke, traffic flow, and crossing assets inside the crossing area.The DTAC coordinates close operations between committed brigades.The DMAIN controls deep fires to isolate the bridgehead from counterattacks.The DREAR sustains the fight.

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Figure 5-2. Division and brigade CP functions


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place after the division continues the attackto subsequent corps objectives. Engineergroups should include one corps combat engi-neer battalion and two AFB companies foreach lead brigade. The corps normally pro-vides a corps engineer light diving team to—

• Conduct nearshore and far-shore recon-naissance.

• Perform bottom-composition surveys.

• Neutralize underwater obstacles.

• Construct underwater bridge structures,obstacles, and floating barriers.

• Perform in-water repair to bridges andwatercraft.

• Recover sunken equipment.

• Search for and recover casualties.

Additionally, the corps normally providesa corps MP company to assist the division

in regulating the traffic and conductingroute security in the crossing area. Thecorps also allocates additional smoke unitsto assist the division chemical company inobscuring the river-crossing area. Finally,the corps will provide short-range air-defense (SHORAD), high-to-medium-altitude air-defense (HIMAD), and air-defense artillery (ADA) support to protectthe bridgehead from air interdiction.

ADVANCE TO THE RIVER (PHASE I)

Once the division has planned the opera-tion, the first phase is initiated (see Chap-ter 4). The division will attack to seizenearshore terrain that includes favorablecrossing sites and road networks. Nor-mally, the division advances with two bri-gades abreast and a reserve brigadetrailing. The cavalry squadron can providea forward or flank screen (see Figure 5-3).The DTAC controls the efforts of the leadbrigades (see FM 71-100).


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The lead brigades attack in zone to seize and secure nearshore objectives.The reserve brigade moves into the AA in the division's rear.The cavalry squadron screens the division's advance.

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Figure 5-3. Advance to the river (division focus)

FM 90-13/MCWP 3-17.1

Well before the division reaches the river, thecavalry squadron moves ahead of the mainbody to conduct a reconnaissance of the nearshore and predetermined crossing sites.Engineer reconnaissance teams may need tobe allocated to the division cavalry squadronto assist in the reconnaissance of crossingsites. If the tactical situation prohibits thecavalry squadron from moving to reconnoiterthe crossing sites, one or both of the lead bri-gades must conduct the reconnaissance. Asthe division arrives at the river, the lead bri-gades establish security on the near shore.The lead brigades develop hasty defensivepositions to protect the crossing area andcover the crossing sites with direct and indi-rect fires.

During the advance to the river, the DMAINcoordinates counterfires, close air support

(CAS), and support of the division aviationbrigade against deep targets. By effectivelyusing these assets, the DMAIN fights thedeep battle and isolates the bridgehead.

The DREAR sustains the division'sadvance. It ensures that key classes of sup-plies are pre-positioned forward. Priority isshifted to the maintenance of the bridgingassets and those of the units supporting thecrossing area.

The BTAC controls the fight of the TFswithin its brigade. The brigade travels in aformation that is METT-T driven. The bri-gade seizes objectives that secure the nearshore (see Figure 5-4).

Each BMAIN is the crossing-area headquar-ters. The crossing area is bounded by RLs


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The attacking brigade leads with two TFs abreast to seize and secure nearshore crossing sites.The TF designated as the main effort prepares to conduct a dismounted assault of the river.The reserve TF moves into an AA to prepare to cross the river and seize the far-shore objective.

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Figure 5-4. Advance to the river (brigade focus)

FM 90-13/MCWP 3-17.1

on the friendly and enemy sides of the river.The RL on the friendly side is usually set 2to 3 kilometers from the exit bank, out ofthe range of enemy direct-fire weapons. TheRL on the enemy side delineates an arealarge enough for forces to occupy battalion-sized attack positions. The BMAIN isresponsible for controlling units that pro-vide the crossing means, traffic manage-ment, and obscuration. Normally, corpsassets are task-organized by the division indirect support of the forward brigades toperform these functions. The BMAIN con-trols these assets. Once the brigade hassecured the near shore, MP and engineersmark routes from the staging area to thecrossing sites; lay out staging, holding, andcall-forward areas; and set up ERPs andTCPs.

Once the near shore is secured, the DTACbecomes the crossing-force headquartersresponsible for coordinating the close opera-tions of the committed brigades within thebridgehead and crossing area. The bridge-head is the area on the far shore that isrequired to provide space and time for thebuildup of combat power to continue offen-sive combat operations. The crossing areais the area, bounded on either side of theriver by RLs, in which units move on prede-termined routes and use the time tablesthat are specified in the division's order.

The DTAC coordinates the efforts of thelead brigades as they prepare to assaultacross the river.

ASSAULT ACROSS THE RIVER

(PHASE II)The DMAIN continues to control deep-fireassets to isolate the bridgehead. As unitsadvance, deep fires shift to subsequent tar-gets. The division coordinates with thecorps for SHORAD and HIMAD coverageto protect the bridgehead from enemy airinterdiction. The corps normally provides

Patriot and Hawk support. The divisionAD battalion provides local AD coverage.The river creates lucrative targets at rela-tively fixed locations that are easily tar-geted by enemy air. Therefore,approaches; holding, staging, and call-for-ward areas; and crossing sites along theriver are the highest priority for AD dur-ing the crossing. AD units occupy positionsto engage aircraft with massed fires beforethe aircraft can reach weapons releasepoints (RPs).

The DTAC coordinates the actions of thebrigades conducting the assault across theriver (see Figure 5-5). The crossing sitesare chosen because of available conceal-ment, a good route system, and sufficientspace for AAs on the near shore. Thesesites also have defensible terrain on thefar shore of the river to provide a securebase for continuing the operation.

The DREAR begins to push packages ofClass IV and V supplies to support thehasty defense to secure the bridgeheadline.

The BTACs control their own respectiveassault-crossing elements, which normallyconsist of dismounted infantry. A corpscombat engineer company, operatingassault boats (RB15s) from the corpsbridge companies, transports the dis-mounted soldiers of the assault force tothe far shore. The dismounted elementcrosses the river and secures terrain forthe reinforcing armored vehicles. Theassault across the river can also be an air-assault operation. The dismounted assaultforces are supported by the tanks andinfantry fighting vehicles from their TFand by other combat units in support-by-fire positions. Heavy rafts are prepared totransport tanks and infantry fighting vehi-cles to the far shore for reinforcing the dis-mounted infantry. M9 ACEs/dozers are


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The lead brigades conduct a dismounted assault across the river to secure a far-shoreobjective, permitting the crossing of armored assets on heavy rafts.

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Figure 5-5. Assault across the river (division focus)

transported to prepare the far-shore exitsites. Rapid reinforcement of dismountedassault forces with armored vehicles may beso critical, based on the METT-T, that it jus-tifies using any expedient method to get thefirst few armored vehicles across. Thisincludes winching, towing, or pushing thefirst ones across normally unsuitable placeswhile engineers improve entry and exitpoints for the rest.

Each BMAIN controls smoke to obscurecrossing sites on the river. Whenemployed, the smoke blanket covers sev-eral kilometers of the river and river

approaches to conceal the actual crossinglocations, but not as to obscure the bridgecrewmens’ vision. The crossing-area head-quarters uses smoke generators, smokepots, and smoke munitions from the divi-sion and corps. The BMAIN controls theuse of MP and corps engineer units toestablish nearshore waiting areas, markroutes to the crossing sites, and begin con-structing heavy rafts and/or bridges.

The intent of this phase is to rapidly placecombat power on the far shore to eliminatethe enemy's direct fire onto the crossingsites and secure terrain for attack positions.


FM 90-13/MCWP 3-17.1

Brigades normally establish limits ofadvance (LOAs) and fire-support coordina-tion lines (FSCLs) for the dismounted TFsconducting the assault. These lines estab-lish an LOA that encompasses the far-shore objective. Enemy indirect fire intothe crossing area will probably continue;however, each crossing site within thecrossing area must be isolated from directfire to enable the construction and opera-tion of rafts. These rafts will then be usedto transport armored vehicles for rapidreinforcement of the dismounted infantryTF. Within the crossing area, securedattack positions allow units to form intocombat formations before continuing theattack.

Commanders may consider immediate con-struction of a bridge during this phasewithout ever conducting rafting opera-tions. The advantage is that combatpower can be massed on the far shore at amuch faster rate. The risk that the com-mander takes in making this decision isthat a large amount of bridging assets isexposed to enemy fire before the elimina-tion of enemy indirect fires on the crossingarea.

ADVANCE FROM THE EXIT BANK

(PHASE III)The division continues its attempt to securethe bridgehead line by attacking to seizeand secure exit-bank and intermediateobjectives. The intent is to eliminate directand observed indirect fires from the cross-ing area (see Figure 5-6).

The division commander selects exit-bankand intermediate objectives based onMETT-T. The river splits the attackingforce, limiting massed direct fires beyondthe exit bank. Therefore, these objectivesare usually smaller and not as far from theattack positions as the objectives used inother offensive operations.

Once the exit banks are secured, the divisioncavalry squadron crosses either by swimmingor rafting their cavalry fighting vehicles.They then conduct normal screening opera-tions for the division as the armored rein-forcements are crossing the river andpreparing to advance from the exit bank.

The DTAC controls the coordinated attack ofthe lead brigades and the cavalry squadronto seize exit-bank and intermediate objec-tives. The DMAIN controls deep fires thataviation, artillery, and CAS provide to blockenemy counterattacks into the bridgehead asrequested by the DTAC.

The DREAR prepares to push packages ofClass III and V supplies that will support theattack out of the bridgehead. They also beginto push Class IV and V supplies for the hastydefense during the last phase of the river-crossing operation.

The BMAINs control the movement oftheir follow-on TFs from the staging areasacross the river to their attack positionson the far shore. They control the upgradeof crossing sites from assaults boats(RB15s) to heavy rafts and/or bridging toensure that the force buildup can supportthe advance from the exit bank to interme-diate objectives. MP and, if available,corps combat engineers assist in move-ment control through the crossing area.

During this phase, limited two-way trafficbegins to return disabled equipment andcasualties.

The BTAC controls the movement out of theattack positions to exit-bank and intermedi-ate objectives. Exit-bank objectives are thosepositions that, when seized, eliminate theenemy's ability to use direct-fire weapons onthe crossing area. Intermediate objectivesare those positions from which the enemycan provide observation for indirect-fire


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The DTAC controls the lead brigades as they pass through the crossing area into secured attack positionswithin the far-shore objective. The lead brigades then attack to seize and secure exit-bank and intermediateobjectives to eliminate direct and observed indirect fires into the crossing area.The BTAC and DTAC reposition forward to maintain control of close operations.

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Figure 5-6. Advance from the exit bank (division focus)

weapons. This enables the expansion ofSHORAD coverage, allowing more time toengage aircraft in air avenues of approach onthe far shore (see Figure 5-7, page 5-10).

The TF that conducted the dismountedassault across the river continues to crossarmored vehicles and remount their dis-mounted soldiers in preparation for contin-ued offensive operations.

The brigade commanders establish theorder of raft loads based on the division'scrossing priorities. Bridge companies runheavy raft sites and begin to construct rib-bon bridges. MP mark routes and control

holding areas on the far shore to ensurerapid transit within the crossing area.

SECURE THE BRIDGEHEAD LINE

(PHASE IV)The bridgehead must be defendable andlarge enough to accommodate forces thatwill break out to continue offensive combatoperations. The lead brigades attack tosecure the final objectives within thebridgehead to prevent the enemy from suc-cessfully counterattacking against forceswithin the bridgehead line by rapidlybuilding enough combat power to establisha hasty defense in the sector. The cavalrysquadron conducts a screen mission. The


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The BMAIN controls the movement of follow-on TFs into secured attack positions on the far-shore. The follow-on TFs then attack to seize and secure exit-bank and intermediate objectives to eliminate direct and observed indirect fires into the crossing area.

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Figure 5-7. Advance from the exit bank (brigade focus)

lead brigades maintain continuous far-shoresecurity to prevent bypassed enemy elementsfrom infiltrating back to the river and dis-rupting activities at the crossing sites (seeFigure 5-8).

The DTAC controls the lead brigades and thecavalry squadron as they secure the bridge-head objectives (see Figure 5-8) and prepareto move the reserve brigade or other corpsforces (breakout forces) into attack positionswithin the bridgehead. Once the bridgeheadobjectives are secured, the lead brigadesestablish a hasty defense in sector.

The DREAR begins to push forward Class IIIand V supplies that are needed for the attackout of the bridgehead.

The BMAIN continues to upgrade and monitor thecrossing sites and control the movement of forcesthrough the crossing area. The far-bank RL, defin-ing the crossing area, is moved just past the inter-

mediate objectives (see Figure 5-8) to providespace for the breakout forces. Once the bridgeheline is secure, the DTAC controls the movement the breakout forces through the crossing area toattack positions within the bridgehead. During thphase, specific bridges and/or rafts are designfor full-time return traffic. This ensures that resupply and the evacuation of wounded soldiers adisabled equipment occur.

The DMAIN controls the aviation, artillery,and available CAS sorties to screen theflanks and interdict enemy counterattacks.Deep operations play a key role in the bridge-head defense by targeting enemy formationsas they move to counterattack. They alsoeliminate effective artillery fire within rangeof the bridgehead and destroy other enemyartillery forces moving up to the fight.

The lead brigade elements that secure thebridgehead line must control the avenues ofapproach into the bridgehead and be large


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Figure 5-8. Secure the bridgehead line (division focus)

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enough to defeat counterattacks. After thebridgehead is secure, the division com-mander commits the breakout force toattack position within the bridgehead. Thebridgehead needs enough space (20 to 30kilometers deep) to accommodate both thelead brigades and the breakout force withtheir combat service support (CSS). Thebridgehead line must also be deep enough toemploy AD systems against hostile aircraftbefore they reach weapons RPs to attackcrossing sites.

CONTINUATION OF THE ATTACK

Once the division has secured the bridge-head, the division river crossing is com-plete. Crossing-area control will be passedto the DREAR and ultimately to the corps.The breakout force must complete its pas-sage before continuation of offensive opera-tions. The lead brigades must reorganizeand prepare to follow the breakout force asthe division or corps reserve. Security

forces from the corps must come forward torelieve the lead brigades from their bridge-head security mission.

As the breakout force crosses into attackpositions, the DTAC begins to focus on theattack out of the bridgehead. Therefore, theDREAR assumes the role of the crossing-force headquarters. This allows the DTACto focus completely on the attack out of thebridgehead, which is usually led by the divi-sion cavalry squadron.

The DREAR controls the breakout force'smovement through the crossing area to theattack positions and two-way traffic facili-tating the return of wounded soldiers anddisabled equipment. The corps must pro-vide other forces for bridgehead securitybefore the lead brigades reorganize toresume their mission as the divisionreserve.


FM 90-13/MCWP 3-17.1

CHAPTER 6

Retrograde OperationsGENERAL

The goal of a retrograde river-crossing oper-ation is to cross a river while preserving theintegrity of the force. A retrograde operationis an organized movement to the rear oraway from the enemy.

This chapter describes only those tacticsand techniques used by a division in a ret-rograde river-crossing operation that aredifferent from those used in an offensivecrossing. A retrograde crossing featurescentralized control at division level.Detailed planning and preparation of engi-neer assets are a critical considerationwithin the time available. A retrogradecrossing differs from an offensive crossingin several aspects:

• Both banks of the river initially areunder friendly control. Accordingly,detailed information concerning theriver and the area over which the retro-grade is conducted should be readilyavailable to the commander.

• All existing bridges and other crossingsites are available to the retrograde forceto expedite the crossing.

• Relative combat power favors theenemy in most cases. Units conductingretrograde operations then mustretain a mobility advantage over theenemy.

Deception is always planned and executedto deceive the enemy and to protect theforce during a retrograde operation. As aminimum, these plans seek to conceal theextent of the operation and the actual cross-ing sites. Smoke, electronic deception, anddummy sites reduce the enemy’s capabilityto disrupt the crossing.

The same control measures are used in ret-rograde operations as in offensive opera-tions. Figure 6-1, page 6-2, shows anexample. See Chapter 3 for a discussion ofeach control measure and a C2 diagram.

RETROGRADE TYPES A retrograde operation may be forced byenemy action or by a higher headquarters.A well-planned, well-organized, and ag-gressively executed retrograde operationprovides opportunities for the division toinflict heavy damage on enemy troops andequipment while continuing to maintain itsfighting integrity. The three types of retro-grade operations are delay, withdrawal,and retirement.

DELAY

Units conduct delays when their strengthis insufficient to attack or defend or whenthey want to maneuver the enemy into an

area for a subsequent counterattack. Adelay is an operation in which the unit,under enemy pressure, trades space fortime by inflicting maximum damage on theenemy without being decisively engaged incombat. Flexible planning allows the unitsconducting a river crossing to adaptquickly to changes during execution. Someimportant features of a flexible planinclude—

• Multiple approach routes from battlepositions to crossing sites.

• Lateral routes between crossing sites.

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• Alternate crossing sites if enemy actionsclose primary sites.

• Crossing equipment held in reserve toreplace losses or open alternate sites.

• Preplanned engagement areas (EAs) toblock enemy advances.

A delay combined with a retrograde rivercrossing has the following phases:

• Delay.

• Crossing.

• Defense.

Each phase is separate only in planning;they overlap during execution. Employingmilitary crossing equipment in the retro-grade is the reverse of the method used in adeliberate, offensive river-crossing opera-tion. Figure 6-2 relates the retrogradesequence to the crossing stages.

Delay Phase

The delay phase provides security for themain body and allows the delaying force togain enough time for the main body toaccomplish its mission (cross the river). Forthis reason, delaying forces take some risk.The delaying force must deceive the enemyand keep it from the river, allowing the

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Figure 6-1. Control measures

6-2 Retrograde Operations

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main body to cross and establish the exit-bank defense.

The division commander establishes a hold-ing line on defensible terrain between theriver and the enemy. Its location precludesdirect and observed indirect fires in thecrossing area.

Forces not assigned tasks in the delay,including those forces with a mission to sup-port crossing areas or establish the defenseon the exit bank, execute a planned retire-ment or withdrawal and cross the river asrapidly as possible. To preclude early enemydetection of the retrograde, the forces followa movement-control plan that supports thedeception plan.

The delay phase continues until the battle iswithin communications and fire-supportrange of the exit-bank defense. The delaying

force must be strong enough to hold theenemy until other forces establish thedefense. The defending force assumesresponsibility for the battle as the delayingforce completes a rearward passage of linesthrough the defending force.

Figure 6-3, page 6-4, shows an example of aretrograde crossing. In this case, the 3rdbrigade is the delaying force. It occupiesbattle positions to the rear of the 1st and2nd brigades at RL Plum, the initial-delayposition (IDP), to help them withdraw. The3rd brigade delays the enemy forward of theholding line until the rest of the divisioncrosses the river and the 1st and 2nd bri-gades reestablish the defense along theriver.

Crossing Phase

In contrast to normal offensive crossingoperations, friendly forces initially control

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Figure 6-2. Retrograde planning


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retrograde crossing sites, which may beinsufficient in number. The enemy usuallyknows where the logical crossing sites areand attacks them early in the operation, butit must not be allowed to capture them.Friendly forces should develop additionalsites to provide flexibility against this possi-bility.

The commander should attempt to salvagetactical bridges and rafts for future use; how-ever, it may be necessary to use them for thecrossing and then destroy them to preventcapture. Fixed bridging must be prepared fordestruction and also be protected againstground and air attacks. This requires closecoordination with the delaying force to pre-clude cutting off friendly forces or allowingenemy seizure of sites intact.

The BMAIN, commanded by the brigade XO(CAC), is responsible for the passage of allunits through the crossing area.

Traffic control up to and through the crossingarea is a critical problem in crossing opera-tions. For this reason, plans for movementmust be detailed, and movement control isessential. This control is exercised by theCAC with assistance from the delaying-forcecommander (brigade commander). The CACcontrols all movement within the crossingarea to include retrograde forces. It is the responsibility of the CAC to ensurethe continuous and orderly flow of the ret-rograde elements across the river. His con-trol includes both the ERPs, which ensurethat all vehicles are of the proper class andsize, and also all waiting areas that feedvehicles through the crossing area. Toassist the CAC, MP and, if available, engi-neers establish and operate TCPs to man-age the traffic flow. CSCs oversee thecrossing means. The CAC and his staffmust synchronize the crossing plan withthe commander's tactical plan.

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Figure 6-3. Retrograde crossing


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Activity within the crossing area begins withtwo-way crossings by CSS units evacuatingnonessential supplies or restocking thedelaying force. During the early stages of theretrograde, the existing crossing means maybe supplemented by tactical bridging. As aminimum, additional tactical bridging assetsmust be planned and available.

Initially, the force crosses on fixed andfloating bridges. It crosses on bridges aslong as possible, since this is the mostrapid means. Once the bridges become vul-nerable to capture, air attack, or observedindirect fires, they may be converted torafts or removed. Vehicles continue to crossby using rafts or by swimming. The cross-ings are made under the suppressive fires ofthe defending force's direct- and indirect-fire weapons.

The forces cross the river in an orderly flowwhile conserving combat power. The retro-grade crossing begins as a rear-area opera-tion for the division. Initially, it is a traffic-scheduling problem, centrally controlledby the division. The division establishescrossing areas before crossing maneuverbrigades. Crossing-area operations are thesame as for offensive crossings (see Chap-ter 5). Even when the division has to estab-lish the crossing areas quickly, underadverse circumstances, it synchronizescrossing-support activities with those ofthe defense force that is preparing to closethe routes in the crossing areas.

Crossing sites need the highest priority forAD. This is particularly critical when theenemy has air superiority or when air parityexists. The sequence for crossing AD unitsshould account for the need to provide con-tinuous coverage of crossing sites.

The division engineers are fully committedto the delay. As a result, engineers underthe control of the CAE run the crossing sites

and support initial preparation of exit-bankdefenses. Engineers focus on enemy engi-neer breaching assets and the interdictioncapabilities needed to support enemymaneuver.

Defense Phase

The defense phase stops the enemy by keep-ing it out of the crossing area, denying itcrossing sites upstream or downstream, anddestroying its attempts to cross the river. Inparticular, the defense phase targets poten-tial enemy crossing assets. Whether continu-ing the retrograde further or defending alongthe river, the division establishes a strongexit-bank defense. The defending force pro-tects the delaying force as it crosses the riverafter battle handover. The rearward passageof lines by the delaying force is a normaldefensive operation, complicated by the river.

Initially, the defending force is small. It con-sists of combat and combat-support units notinvolved in the delay as well as augmenta-tion from corps reserves. Because enoughforces are not available to defend all pointsalong the river, the defense depends on rapidlateral movement to concentrate at vulnera-ble points. In particular, it orients on andprotects the crossing sites against theenemy’s forward detachments and heliborneforces.

After battle handover from the delayingforce, the defending force is responsible forthe area between the holding line and defen-sive positions on the exit bank. The defend-ing force masses fires to help its elements incontact forward of the river to withdraw,thereby complicating the retrograde crossing.

The defending force accepts battle hand-over from the last of the delaying force atthe holding line and covers its crossingover a fixed bridge that is prepared fordemolition. Friendly forces at the river pre-vent the enemy from crossing at the site of


FM 90-13/MCWP 3-17.1

a demolished fixed bridge so that compa-nies securing the crossing site can safelywithdraw in turn.

WITHDRAWAL

A withdrawal differs from a delay in that itis an operation in which the unit in contactdisengages from an enemy force and movesto the rear. Withdrawals are executedwhen the commander desires to withdrawto control future tactical operations with-out being forced to do so by enemy pres-sure. A withdrawal follows the samesequence as a delay. The only difference isthat the unit may or may not be in enemycontact.

During a withdrawal, the enemy usuallydoes not pressure withdrawing units. Also,other friendly units do not normally assistin withdrawals. Care must be taken toensure that the enemy does not try to iso-late and encircle units during river-crossingoperations. If a unit has difficulty breakingwith the enemy in a withdrawal, it canrequest help from a higher level. Theassisted withdrawal will be a rearward pas-sage of lines. Exchange of information on

obstacles, indirect-fire targets, and routes inthe sector must be coordinated before con-ducting the passage of lines. The assistingunit provides mobility support along clearedroutes and corridors in its sector for thepassing unit.

Engineers must complete clearing opera-tions before the passage begins. The assist-ing unit also closes the lanes once passage iscomplete. The passing unit must plan andorganize for conducting internal breachingand river-crossing operations before initiat-ing the passage of lines. This should ensureresponsive mobility operations if the enemyblocks routes during the passage.

RETIREMENT

Retirements are rearward movementsaway from the enemy by a force not in con-tact. Typically, another unit's securityforces cover their movement as they con-duct a tactical road march. A retirementfollows the same sequence as a delay.Speed is important; therefore, engineersshould focus on mobility for the retiringunit and expect operations such as routeclearance and route repair.

DENIAL MEASURESDenial measures are actions taken to hinderor deny enemy use of resources or facilities.In retrograde crossings, the commanderincludes bridges and crossing sites in hisdenial measures.

The laws of war require that denial opera-tions, particularly against civilian resourcessuch as existing bridges, be carefully consid-ered and that execution authority to destroythe structure be maintained at the highestlevel.

A defending-force commander is responsiblefor preparing existing bridging and othercrossing means in his sector, such as ferries,for destruction to prevent their use by the

enemy. The CAE controls the engineers whoprepare those targets. The timing of theirdestruction depends on their use in support-ing the crossing. When the tactical situationdictates that crossing sites are no longerneeded or the risk of capture outweighs theirusefulness, the defending force must destroythem.

Use of bridges in the retrograde requires aredundant means of bridge destruction and arobust demolition guard with an engineerdemolition party (see FM 5-250). Engineerlight diving teams can be used to survey andemplace, prime, and detonate explosives onbridge supports to deny enemy access duringretrograde operations. Because of the severe


FM 90-13/MCWP 3-17.1

consequences of a premature decision todestroy a site, the division commander usu-ally designates sites as reserve targets andissues specific orders stating under what con-ditions and by whose authority this destruc-tion can be done.

Engineers destroy military bridges thatthey cannot recover quickly. Bridge stocksare in short supply; therefore, if existingbridges are sufficient to support the retrograde,

the engineers recover military bridges early.In addition, the denial of major existingbridges can be so important that the com-mander may choose to destroy them earlyand rely on military bridges to cross theremainder of his force. The ribbon bridge ispreferred for this crossing because of itsrecovery speed. Engineers either recoverlines of communication (LOC) bridges wellbefore the enemy arrives or destroy thoseleft in place after the delay.

PLANNINGThe division commander identifies the hold-ing line and the units required to fight thedelay and defense battles. The division engi-neer, in conjunction with the G3, identifiescrossing sites and required crossing assets.The division staff coordinates for additionalcorps assets. The staff uses the planningprocess identified in Chapter 4.

The commander uses deception to concealthe extent of the operation and the actualcrossing sites. Smoke, electronic warfare,and dummy sites reduce the enemy’s capa-bility to disrupt the crossing. OPSEC keepsthe enemy-intelligence collectors from iden-tifying the time and place of the crossing.

The commander may consider retainingfixed bridges in defense of the river line ifhe anticipates future counterattacks backacross the river. He may also partiallydestroy bridges to ease restoration infuture offensive operations, weighing thisdecision against the enemy’s use of thebridges.

Denial operations are somewhat restric-tive. Only those civilian targets with aclearly identified military value can bedestroyed or removed. Coordinationbetween the theater command and thehost-nation government is important in thepolicy-development process.


FM 90-13/MCWP 3-17.1

CHAPTER 7

Crossing Sites GENERAL

The following paragraphs supplement thegeneral descriptions of acceptable crossingsites in Chapter 2. Selection of crossing sitesis primarily based on the—

• Existing situation and anticipatedscheme of maneuver.

• Physical characteristics of the availablesites, road networks, and surroundingterrain.

• Availability and capabilities of crossingmeans.

• Availability of engineer support.

Conflicts between tactical and technicalrequirements frequently occur. Command-ers evaluate the factors bearing on theproblem to determine the best overall solu-tion.

CROSSING-SITE SELECTIONEach crossing means, except air assault,requires a type of crossing site. They can beidentified as fording, assault-boat, swim-ming, rafting, or bridging sites. Assault bat-talions use either a fording or an assault-boat site (or sometimes a swimming site) asan assault site.

Both the desired scheme of maneuver andavailable crossing means influence crossing-site selection. The division assigns a cross-ing area to each lead brigade. The brigadechooses which crossing sites to use withinits area. When a particular site is importantto the division's tactical concept, such as forthe movement of breakout forces, the divi-sion either coordinates with the affected bri-gade to open that bridge site or moves abridge to that site once the brigade handsover the crossing area to the division.

Brigade commanders select final crossingsites based on tactical intelligence and theirdesired schemes of maneuver. Each site'sphysical characteristics, required engineersupport, and available crossing means influ-ence the decision, but tactical requirementsare the most important.

The goal when selecting assault sites is topick those that allow the lead battalions tocross unopposed and seize far-shore objec-tives rapidly. If unsuccessful at findingundefended crossing sites, the lead battal-ions cross under enemy fire while over-watch units provide direct and indirectsuppressive fires. Assault sites may ormay not coincide with rafting or bridgingsites.

When selecting swimming sites, the goal isto pick those that permit fighting vehicles torapidly enter, swim across, and exit thewater with minimum assistance.

The goal when selecting rafting and bridg-ing sites is to pick those that support thegreatest volume of vehicle traffic consis-tent with the scheme of maneuver. Raftingand bridging sites are usually on or nearmajor roads to minimize route preparationand maintenance. When the sites arelocated close together, the bridging sitemust be upstream of the rafting site. Thiswill avoid potential damage that may becaused by disabled rafts drifting into thebridge.

Crossing Sites 7-1

FM 90-13/MCWP 3-17.1

Regardless of the crossing means, each siteneeds engineer reconnaissance swimmers oran engineer light diving team to cross early,reduce obstacles, and develop exit points onthe far bank. Riverbanks at otherwise suit-able crossing sites often need work foraccess to the river. Most natural soilbecomes unstable under heavy traffic. Thiscondition worsens as fording, swimming,and rafting activities carry water onto it.The required engineer effort varies with soiltype, crossing means, and vehicle density.An engineer vehicle that is capable of main-taining the exit bank should be one of thefirst vehicles across.

Natural conditions vary widely. Banks mayrequire little preparation, or they may be sorestrictive that they limit feasible sites.Desirable site characteristics include—

• Minimum exposure to enemy direct-fireweapons.

• Covered and concealed access to theriver's edge.

• Firm and gently sloping banks thatallow rapid entry and exit at multiplepoints.

Initial and subsequent entry points canvary. Available locations seldom have all thedesired tactical and technical characteris-tics. The best routes through the crossingarea normally cross the river at the techni-cally best crossing sites. The best technicalsites may not be the best tactical sitesbecause they are well known and areheavily defended by the enemy. Forces ini-tially crossing at less desirable locations aremost likely to avoid detection and gain sur-prise. Moving laterally along the exit bank,forces attack the flank or rear of enemyunits to seize the better crossing locations.Use of these sites allows rapid buildup ofcombat power.

PLANNINGPlanners need information of potentialcrossing sites to evaluate their compatibilitywith proposed crossing plans. Generally,planners need to know—

• Friendly and enemy capabilities andprobable COAs.

• Site capacity for the crossing of troops,equipment, and supplies using variouscrossing means.

• Engineer support that is required todevelop, improve, and maintain each site.

More specifically, planners need to knowthe—

• Condition of the bottom, banks, andwater of the river.

• Impact of forecasted or past seasonalweather conditions.

• Location of defensible terrain, coveredand concealed areas, and natural orenemy-emplaced obstacles on both sidesof the river.

• Amount of time and effort that isrequired to develop sites, assemble rafts,and construct bridges.

• Entry/exit routes and off-road trafficabil-ity.

• Road networks.

• Capabilities of friendly forces to denyobservation, suppress fires, and providesite protection.

REQUIREMENTSDiscussed in the following paragraphs aresome of the requirements necessary forcrossing sites.

ENTRY/EXIT ROUTES OR PATHSA desired feature of all sites is readily acces-sible entry/exit routes or paths on either

7-2 Crossing Sites

FM 90-13/MCWP 3-17.1

bank. The approaches to the banks arechecked for their ability to support therequirements (width, slope, and trafficabil-ity) of the wheeled and tracked vehicles ofthe crossing element. Covered and concealedapproaches enhance surprise and surviv-ability; however, multiple routes, free fromobstruction, will increase crossing speed andflexibility. Exit-bank conditions often takeprecedence over entry-bank conditions untilequipment and troops can be crossed todevelop and improve the site. See Table 7-1for depth requirements.

ROUTES AND APPROACHES

Depending on the crossing operation that isused, the following considerations must begiven to routes and approaches:

• Fording. Dismounted forces may useapproaches with steep slopes and heavyvegetation, while vehicle fording requirespaths or roads to approach fording sites.

• Assaulting or swimming. Assault-boatcrossings may use more ruggedapproaches than amphibious vehicles.

• Rafting. Multiple approach routes torafting sites permit the relocation ofrafting upstream or downstream.

• Bridging. Bridging sites require devel-oped road networks to sustain the cross-ing capacity.

Depending on the vehicle that is used, thefollowing considerations must be given toroutes and approaches:

• Wheeled vehicles. In general, wheeledvehicles require 3.5-meter path widthsand 3.5 meters of overhead clearance.Dry, hard slopes of 33 percent can benegotiated; however, slopes less than 25percent are desired.

• Tracked vehicles. Tracked vehiclesrequire up to 4-meter path widths and3.5 meters of overhead clearance. Tankscan climb 60 percent (31-degree) slopeson dry, hard surfaces; however, slopesless than 50 percent are desired.

WAITING AREAS

Numerous waiting areas are required forequipment and troops preparing and pro-tecting sites and for troops and vehicles pre-paring and/or waiting to cross. These areasshould be dispersed, provide cover and con-cealment, and be accessible to road net-works near the sites.

Table 7-1. Depth requirements

Operation ItemDraft in Meters Remarks

Fording Personnel 0.10

Wheeled vehicle 0.75

Tracked vehicle 1.20

Assaulting/swimming

M113 (APC) 1.50 The water should be deep enough for the vehicles being used.

M548 2.00

M2 1.07

Rafting/bridg-ing

Power boat (27 feet) 1.00 The water should be deep close to the bank to preclude ground-ing of the raft or bridge.

LTR 0.60*

M4T6 0.75*

Ribbon 0.60*

NOTE: *Power boat draft may govern depth.

Table 7-1. Depth requirements

Crossing Sites 7-3

FM 90-13/MCWP 3-17.1

RIVER CONDITIONS

In general, currents less than 1.5 metersper second (MPS) are desired. Narrow seg-ments of the river decrease equipmentrequirements, crossing time, and exposuretime. However, resulting increased currentvelocities may offset any advantage. As thecurrent’s velocity increases, it decreases theribbon bridge's ability to handle heavy mili-tary load class (MLC) vehicles. More boatswill be required to keep the bridge in placeand allow for heavy MLC vehicles to cross.

BANKS

Ford banks may be steep and rugged for dis-mounted troops; however, vehicles requireslopes less than 33 percent and firm soilconditions. Assault or swim banks may besteep when using assault boats for dis-mounted troops. Amphibious vehicles maybe able to enter over low, 1-meter verticalbanks, but they require sloped exits. Verti-cal banks of about 1 meter may be accom-modated by bridge or raft ramps (see Table7-2). Vertical bank heights for bridges usingthe equipment listed in the table do notchange for ribbon bridges. For M4T6 andClass 60 bridges, the height of the bridgedeck can be adjusted to accept a differencein bank heights; however, the limiting fac-tor may become the longitudinal slope ofthe bridge.

BOTTOMS

Ford bottoms must be free from obstacles,firm, and uniform. Riverbeds may beimproved with rock fill or grading equip-ment. Guide stakes make the crossing ofthe river easier for boat drivers. Assault- or

swim-site bottoms must be free fromobstructions that interfere with boats orthe tracks of amphibious vehicles. Raftingsites must be free from obstructions thatcould interfere with boat operations.Bridges emplaced for lengthy periods (4hours or more) or in strong currentsrequire suitable riverbeds for anchorage.Engineer light diving teams from the corpsArmy may be used to—

• Conduct river-bottom reconnaissance.

• Emplace shore and midstream anchor-age for debris and antimine andantidiver nets to ensure the success ofthe operation.

ENEMY SITUATION

Sites masked from enemy observationenhance surprise and survivability bydegrading the enemy’s ability to see. Usingexisting sites reduces preparation time butrequires caution in that the enemy mayhave emplaced obstacles and registeredartillery on the site.

SITE ANALYSISA ground reconnaissance refines and con-firms information gathered from othersources. Training Circular (TC) 5-210 con-tains details for conducting and reportingsite reconnaissance. From this and other

detailed reports, planners may developcharts or overlays to compare alternatesites. Unit SOPs may prescribe specificcomparative methods. See Figure 7-1 for anexample.

Table 7-2. Bank requirements

Equipment Ramp Articulation (raft)

Up Down

M4T6 Not adjustable

Class 60 Not adjustable

Ribbon 1.7 meter*

NOTE: *An approach ramp 2.1 meters (7 feet) long provides extra roadway for loading and off-loading vehicles.

Table 7-2. Bank requirements

7-4 Crossing Sites

FM 90-13/MCWP 3-17.1

FIELD CALCULATIONSSome common relationships and field-expedient calculations that are useful dur-ing a ground reconnaissance include—

• Measuring the current’s velocity.

• Determining slopes and degrees.

• Measuring the river’s width.

• Calculating downstream drift.

MEASURING THE CURRENT’S VELOCITY

Correlating the desired maximum currentvelocity of 1.5 MPS with a familiar compar-ative unit of measure may help in estimat-ing the current’s velocity. The quick-timemarch rate of 120 steps per minute, with a

30-inch (or 76-centimeter) step, equates to1.5 MPS. Other approximate correlations of1.5 MPS include—

• 5 feet per second (fps)

• 3.5 miles per hour (mph)

• 5.5 kilometers per hour (kph)

Determining the current’s velocity is criticalto effective and safe crossing operations.When it is high, more boats are required tostabilize the bridge, particularly whenanchorage is not used. A reasonable estima-tion involves measuring a distance alongthe riverbank and noting the time a floatingobject takes to travel the same distance.

Bank Preparation Time

• Describe the height, slope, and stability of the bank.

• List the amount of time and effort required to overcome signifi-cant natural and enemy-emplaced obstacles.

• Include day, night, or other reduced-visibility constraints.

River Conditions

• Specify the width, depth, velocity, and bottom conditions of theriver, as appropriate.

• Include variations or unique factors (such as sandbars, turbu-lence, or water depth at the bank).

Vegetation

• List areas suitable for work sites and AAs and available coverand concealment.

Full Crossing Rate

• Describe foot-, wheeled-, and tracked-movement capabilities onroads, trails, and cross-country.

• Describe the maximum crossing rate for fording, swimming, orrafting.

• Include the overall assessment of the crossing site’s potential.

Figure 7-1. Crossing-site requirements

Crossing Sites 7-5

FM 90-13/MCWP 3-17.1

Current

Floatingobject

Shoreline

A B

Example :Measure AB.Throw a stick or another floating object upstream ofthe starting point D.

Record the time the object floats from D to E.

Current = Distance AB (meters)Time DE (seconds)

D E

Dividing the distance by the time providesthe current’s velocity (see Figure 7-2).

DETERMINING SLOPES AND DEGREES

The slope of terrain is significant (for exam-ple, slopes of 7 percent or more slow move-ment and may require vehicles to operate ina lower gear). Slope, usually expressed as apercentage, is the amount of change in ele-vation (rise or fall) over a ground (horizon-tal) distance (see Figure 7-3).

The means to determine the percent of theslope include—

• Clinometers. These instruments mea-sure the percent of the slope and areorganic to most engineer units down tothe platoon level.

• Maps. In this method, first measure thehorizontal distance along the desiredpath, then determine the difference inelevation between the starting and end-ing points of the path. The next step is toensure that both figures are the same

unit of measure (such as meters or feet).The final step is to divide the elevation(rise) by the distance (run) and multiplythe result by 100 to get the percent ofthe slope (see Figure 7-4).

Figure 7–2. Measuring the current’s velocity

Figure 7–3. Slope calculation

Verticalchangeor rise

Horizontal distance or run

Formula:

The rise divided by the run multiplied by 100 equalsthe percent of the slope.

(% slope = rise/run x 100)

NOTE: The rise and the run are expressed in thesame unit of measure (meters or feet).

Rise = 165 - 120 = 45 metersRun = 200 meters% slope = 45 x 100 = 22.5% 200

0 100 200 m

120

140

160

Figure 7–4. Terrain slope

7-6 Crossing Sites

FM 90-13/MCWP 3-17.1

A

B

Far shore

Near shore

Current's velocity (A)

Crossing speed (B)x the river's width (C) = downstream

drift (D)

NOTE: All measurements must be in the same unit ofmeasure (meters or feet).

C

D

• Line of sight and pace. This method usesthe eye-level height above ground (usu-ally from 1.5 to 1.75 meters) and thelength of standard pace (usually 0.75meters). While standing at the bottom ofthe slope, the individual picks a spot onthe slope while keeping his eyes level.He paces the distance and repeats theprocedure at each spot. Adding the verti-cal and horizontal distances separatelyprovides the total rise and run.

Slope may also be expressed in degrees;however, this provides angular measure-ments. The method is not commonly usedbecause the relationships are more complexthan desired for field use. Figure 7-5 listssome relationships of the percent of theslope to the degree of the slope.

MEASURING THE RIVER'S WIDTH

A field-expedient means of measuring theriver's width is with a compass. Whilestanding at the waterline, fix your sight on apoint on the opposite side and note the mag-netic azimuth. Move upstream or down-stream until the azimuth reading to thefixed point on the opposite bank is 45degrees different than the original reading.The distance from the original point to thefinal point of observation is equal to theriver’s width (see Figure 7-6).

CALCULATING DOWNSTREAM DRIFT

Current causes all surface craft to drift down-stream. Each vehicle has a different formulafor calculating downstream drift. Amphibi-ous vehicles and assault boats drift more

than powered boats and rafts; the latter hasa greater capability to negate the effect of thecurrent’s velocity by applying more power.

Amphibious vehicles and nonpowered assaultboats are generally limited to current veloci-ties of 12.5 to 2 MPS and 1 MPS respectively(see Figure 7-7).

Slope Degrees100% 60% 40% 20%

45312211

Figure 7–5. Relationship of slopes

Figure 7–6. River’s width

Figure 7–7. Amphibious drift

Far shore B

C A D

55o 325o

45o 45o0o

Original observation from A to B reveals 0azimuth. Move toward either C or D. Whenthe azimuth is 45 degrees different, thedistance AC or AD equals AB (the river's width).

to degrees

Crossing Sites 7-7

FM 90-13/MCWP 3-17.1

When crossing with amphibious vehiclesand pneumatic boats, compensate for theeffect of the current (see examples below).

Example 1

Entry is usually made upstream of thedesired exit point. The vehicle or boat isaligned, or aimed, straight across the river,creating a head-on orientation that is per-pendicular to the exit bank. However, thecurrent produces a sideslip, downstreamforward movement (see Figure 7-8). Thistechnique requires operator training in con-tinual adjustment to reach the objectivepoint on the exit bank. This techniqueresults in a uniform crossing rate in theleast amount of time and is usually thedesired technique.

Example 2

If the operator continues to aim the vehicleat the desired exit point, the orientation ofthe craft at the exit point will approximatean upstream heading. The craft’s path is anarc in proportion to the current’s velocity(see Figure 7-9).

Example 3

To exit at a point directly across from theentry point requires an upstream heading to

compensate for the current’s velocity (seeFigure 7-10).

In all three examples, the craft's speed rela-tive to the current’s velocity is constant,assuming the engine revolutions per minute(rpm) or paddling rate remains constant.

Far shore

Current

Exit

Far shore

Current

Entry

Exit

Far shore

Current

Entry

Figure 7–8. Downstream sideslip

Figure 7–9. Constant aim point

Figure 7–10. Constant heading

Entry

Exit

7-8 Crossing Sites

FM 90-13/MCWP 3-17.1

Terrain conditions may restrict the locationof entry and/or exit locations. Enemy situa-tions may require alternate techniques. Forexample, when aiming at the downstreamexit point, the craft moves at a greater speedrelative to the banks after entry than it does

as it nears the exit due to the current’s veloc-ity. Use of this technique may be favoredwhen the enemy has a better observation ofthe entry bank rather than the exit bank.Watercraft moving fast and at a changingrate are more difficult to engage effectively.

RAFTSThe assault force seizes a far-shore objec-tive and then clears in zone to secure thecrossing sites from direct fire. Quick rein-forcement with armored fighting vehicles iscritical when the initial assault is dis-mounted.

Given the vital need to rapidly build com-bat power on the far shore, the lead bri-gades should swim the fighting vehicles ofthe follow-on battalions whenever practicalto save the rafts for the tanks. Rafts areusually the initial means for crossing non-swimming vehicles, particularly tanks, onwide, unfordable rivers. It may be possibleto bridge immediately after the assaultacross the river; however, rafting is nor-mally first because rafts—

• Are less vulnerable to enemy air andindirect fire due to their size and maneu-verability.

• Are quicker to assemble.

• Offer more flexibility in operation, par-ticularly in site selection and subsequentmovement between sites.

• Can use existing road networks andbanks where access and exit routes arenot aligned opposite of each other.

Raft assembly begins on order, not accord-ing to a preplanned schedule, even thoughthe crossing plan has an estimated starttime. Unless the division commanderdirects otherwise, the brigade commander,advised by his CAE, decides when to beginrafting. This is always after eliminatingenemy direct fire on the site and usually

after neutralizing observed indirect fire.Massed enemy indirect fire can cover anentire rafting site. The force neutralizesobserved indirect fire by suppressing it andobscuring the crossing sites.

SITE PREPARATION

The brigade commander also decides whenbank preparation can begin, or he may dele-gate this decision to his CAE. The decisionis based on the estimated time required tosecure the area. By initially spending extratime and effort preparing a bank, mainte-nance problems can be avoided during raft-ing operations.

The key to rapid and effective bank prepa-ration is good engineer reconnaissance,which permits engineers to arrive at the siteearly, organized and equipped to performspecific tasks to improve the approach. Thesame is true on the exit bank. Poor bankconditions require early priority for raftmovement of engineer equipment across theriver. Time spent preparing the exit banksbefore passing heavy traffic greatly reducesmaintenance of the crossing site and speedsforce buildup later. Two entry and exitpoints per centerline make it possible toalternately use one while maintaining theother.

RAFTING SITES

Each lead brigade should have at least tworafting sites, each of which has one to threeraft centerlines. The terrain, routes, andtactical plan determine their location. How-ever, they should not be closer together than300 meters to avoid congestion and the risk

Crossing Sites 7-9

FM 90-13/MCWP 3-17.1

that enemy artillery concentrations willimpact on more than one site during a bar-rage. Engineers prepare alternate sites assoon as possible to permit the relocation ofrafts in case of enemy action or bank deteri-oration. Each rafting site also contains thecontrol and operation structure that is nec-essary to conduct rafting operations (seeFigure 7-11).

Engineer platoon leaders are in charge ofrafting sites. Each site has one to threeactive centerlines spaced 100 to 300 metersapart. With the 100-meter minimum dis-tance between centerlines, collisionsbetween rafts on adjacent centerlines areavoided and the effects of artillery are

reduced. However, spacing centerlines far-ther than 300 meters apart stretches theability of one’s unit to control both landapproaches and water operations. Eachcrossing site has at least one alternate cen-terline. The CSC switches to the alternatecenterline when necessary due to enemyfire or bank maintenance.

The centerline has an embarkation pointon the near bank, a debarkation point onthe far bank, and rafts operating betweenthese two points. The number of rafts on acenterline depends on the river's width andthe unit's control (see Appendix C). Main-taining bridge-unit integrity on center-lines and crossing sites is critical. It

7-10 Crossing Sites

Current

Alternate

Centerline

Safety line

Safety boat

Site commander

Raft-maintenancesite

Holdingarea

Call-forwardarea

EEP

Holdingarea

Centerline

centerline

Unit-maintainancecollectionpoint Hospital/aid station

Figure 7–11. Rafting site

FM 90-13/MCWP 3-17.1

simplifies the maintenance and operation ofrafts and significantly improves control onthe water, as all raft commanders and boatoperators have trained together. On any cen-terline, rafts must be the same type and con-figuration.

Centerlines are marked to guide vehiclesapproaching and leaving the water and toguide rafts to the correct landing points.Marker stakes or panels are used duringdaylight, and dim lights (covered flashlightsor chemical lights) are used at night (seeFigure 7-12). The raft commander desig-nates the location of the markers dependingon the terrain and the current’s velocity.Markers include the following:

• Raft-guide markers, at a 45-degree angleupstream, are used to guide the raft to

the embarkation or debarkation point.The two markers are 91 centimetersapart, and the marker farthest from theriver is 60 centimeters higher than theother. The raft has the correct approachto the bank when the markers appear tobe in a straight line, with one above theother.

• Raft-landing markers depict the leftand right limits of the embarkation ordebarkation point.

• Vehicle-guide markers are used to alignraft loads with the raft and are visible toboth the raft and the vehicles.

Each rafting site contains at least one safetyboat, normally a bridge-erection boat (BEB),for troop and equipment recovery. The bridge

Crossing Sites 7-11

Raft-guide markers

Raft-landing markers

Vehicle-guide markers

1.5 m

1.5 m

91 cm3 m7.6 m

Current

7.6 m 3 m 91 cm

1.5 m

1.5 m

Figure 7–12. Centerline marking and operation

FM 90-13/MCWP 3-17.1

company provides a crew for the safety boat,including a boat operator, a boat commander,a medic, and a lifeguard (two, if possible).The lifeguard-qualified swimmer does notwear boots or load-bearing equipment (LBE).The safety boat also has a float with anattached line for rescuing troops in thewater, a boat hook, rocket-propelled lifelines(if available), and night-vision goggles (forthe boat commander, primarily). It has aradio on the bridge company net. The safetyboat maintains its station 50 meters down-stream of the rafting site.

As soon as possible, a safety line should berun across the river 100 meters down-stream from the last centerline. This line isfastened to the banks and kept afloat by lifejackets attached to the line every 30meters. This rope acts as a catch rope fortroops who may fall overboard during raft-ing operations, especially during limitedvisibility. The safety line does not replacethe need for a safety boat but helps in caseseveral soldiers fall into the river.

Each crossing site requires an EEP locatedwhere the equipment will be accessible tothe crossing site. Traffic between the EEPand the riverbank should use a separateroute to avoid congestion with the crossing.

Each rafting site requires a place along thefriendly shore, downstream of the center-lines, for immediate raft repairs. The main-tenance area requires an access point to theriver for the removal and launching of baysand boats. Additional equipment desired atthe maintenance area includes—

• A bridge boat to move damaged bays andserve as a spare boat.

• A crane to remove nonrepairable equip-ment from the water.

• A bridge truck to transport damagedequipment to the EEP.

• A fuel heavy-expanded mobility tacticaltruck (HEMTT) to refuel boats.

• One or more interior and exterior bays touse as replacement parts.

The maintenance area is continuouslymanned with—

• Two mechanics with tool boxes.

• Two fuel handlers.

• The operators of the various pieces ofequipment.

• A site supervisor.

RAFTING OPERATIONS

Units begin their preparations for raftingoperations at a staging area. There, theyreceive briefings, conduct inspections, andrehearse the rafting operation. Personnelwill be issued life jackets and given instruc-tions on what to do upon loading onto theraft.

When ordered to begin rafting, the site com-mander directs personnel at the ERP in thecall-forward area to begin sending raft loadsforward. Units proceed from a staging areato the call-forward area where engineers atthe ERP organize them into raft loads andsend them down to the river. Any pointsalong the route that may cause confusion,such as intersections, are either mannedwith a guide or are marked to ensure thatthe vehicles do not get lost. Once a raft loadnears the river, the platoon leader directs itto the appropriate centerline. The platoonleader controls the flow of traffic to the cen-terlines to ensure that there is a smoothflow of traffic and that centerlines are nei-ther congested nor underused. He estab-lishes the timing required so that raft loadsleave the call-forward area and match upwith a returning empty raft.

When a raft load reaches the riverbank, itis met by an engineer centerline guide. Hestops the raft load 3 meters from the edge

7-12 Crossing Sites

FM 90-13/MCWP 3-17.1

of the water and holds it there for the raftcommander. The raft commander guidesthe vehicles of the raft load onto the raft.The raft crew chocks the vehicles andensures that all passengers are wearinglife jackets. The passengers do not dis-mount from their vehicles. All hatches areopened to allow quick exit of the vehicle incase of an emergency. Upon reaching thedebarkation point, the raft commanderguides the vehicles off the raft. After theraft load debarks, the raft commanderchecks with the centerline guide for anyreturn vehicles and returns to the embar-kation point.

Once on the far shore, the centerline guidedirects the raft load to the far-shore holdingarea where it re-forms. The passengersremove their life jackets, which are collectedand returned by an engineer team to thestaging area for future loads.

MAINTENANCE AND REFUELING

During rafting operations, rafts requirestops for refueling, preventive maintenance,and minor repairs. The efficiency of thecrossing depends on all rafts having enoughfuel and minimal lost time for refueling andnormal maintenance. This efficiencyrequires the bridge company to intenselymanage raft maintenance and to operatethe maintenance area much like a pit crewin an automobile race. When directed, a raftpulls off the centerline and moves to thecrossing-site maintenance area.

With the raft secured, the crew begins refuel-ing and maintenance operations. Mechanicsassess and repair any minor damages to theraft and the boats. Fuel handlers run fuel

lines from the fuel to both bridge boats andfuel them simultaneously. If no major defi-ciencies are identified, the entire processrequires 20 minutes. If major deficiencies areidentified on the boat, it is removed from theraft and replaced with an awaiting spare.The boat will then be removed from thewater and sent back to the EEP for repair.When refueling and maintenance operationsare finished, the raft returns to its centerlineand another raft is directed in for mainte-nance and refueling.

Since the maintenance and refueling opera-tion is continuous and requires removing araft from the operation for up to 30 minutes,it is important to account for this reductionin capabilities when planning the operation.Generally, it is unnecessary to refuel for thefirst two hours after rafting begins. Onceraft maintenance and refueling begin, one ofthe six rafts in each bridge company isunavailable for carrying vehicles across theriver at all times.

When a raft becomes damaged and needsimmediate repair, the raft commandermoves it to the maintenance area. If a raftloses a boat and cannot make it to the main-tenance area without assistance, the raftcommander contacts the maintenancesupervisor, who sends the maintenance boatout to assist. If a raft is still carrying a load,the raft commander decides on which bankhe will disembark the load. Once in themaintenance area, mechanics determine theextent of the damage. If the damagerequires significant repair, the raft will beremoved and replaced with a spare.Lengthy equipment repairs are done at theEEP.

BRIDGESBridges replace or supplement rafts onceenemy-observed indirect fire is eliminated.Each lead brigade should convert at least onerafting site to a bridge site as soon as possible,

while keeping other rafting sites in operationuntil a second bridge is in place. Bridges havegreater traffic-flow rates than rafts. The rib-bon bridge is the preferred initial bridge,

Crossing Sites 7-13

FM 90-13/MCWP 3-17.1

since it is faster to assemble and easier tomove than other types. Once assembled, allfloat bridges have a crossing rate of 200 vehi-cles per hour, with a vehicle speed of 15 mph.As with rafts, bridge assembly begins onorder, not according to a preplanned sched-ule. Since vehicles cross rivers much fasteron bridges than on rafts, early bridge assem-bly is desirable but must be weighed againstthe risk that the enemy can still bring indi-rect fires down on an immobile bridge. Thebrigade commander decides when to begin,with advice from his engineer. He may dele-gate this decision to his CAE.

Bridges need protection. AD, counterfires,and ground-security elements are neces-sary to defeat enemy attacks. Booms on theriver protect bridges from damage caused bywaterborne munitions and debris. Antidivernets are placed upstream and downstreamto protect bridges from swimmers or under-water demolition teams. Engineer light div-ing teams may be employed to reduce debrisalong the debris-collection side of theupstream boom using portable hydraulicchain saws.

Bridges are vulnerable to enemy long-rangeartillery fire and air attack even after theassault force clears enemy forces from theexit bank. For this reason, ribbon bridgesare used for a limited period of time, nor-mally two to four hours, before engineerbridge units break them apart and movethem to other sites. When the division usesthis pulse-bridging tactic, its units wait tocross in staging areas and surge acrosswhen bridges are in place.

Enemy air superiority over the river mayprohibit bridge assembly. A sustainedenemy air attack forces engineers to breakestablished float bridges into rafts. Thisminimizes the destruction of scarce bridgingassets yet enables the crossing to continue,though at a slower pace. Engineers prepare

alternate sites and position spare equip-ment nearby in case of enemy action.

As the danger from enemy action lessens,engineers use the more slowly assembledLOC and M4T6 bridges to augment andthen replace the tactical bridges (ribbonbridge or AVLB). They do this as soon aspossible to move ribbon bridges forward toother crossing operations.

Enemy bridges captured by the lead bri-gades are a bonus and speed the crossing.Engineers with the lead brigades neutral-ize explosive devices and reinforce weak ordamaged bridge structures whether thedamage is above or below the waterline.Commanders rarely base the success of anoperation solely on the seizure of intactbridges.

SITE ORGANIZATION

A bridging operation requires a continuoustraffic flow to the river. Units must be quicklybriefed and moved to the crossing site. Toaccomplish this, units receive briefings in thestaging areas from traffic-control personnel.There is no intermediate call-forward area.To control crossing vehicles, the engineersfrom the bridge unit set up an ERP at thebridge’s access points on each side of theriver. These engineers guide vehicles ontoand across the bridge, ensure the properspeed and spacing of vehicles on the bridge,and prevent vehicles too heavy for the bridgefrom trying to cross.

A recovery team is stationed on the farshore to remove any damaged vehicles fromthe bridge. The recovery team consists of amedium or heavy recovery vehicle and crew,with sufficient winch cable to reach acrossthe bridge. A typical site setup is shown inFigure 7-13. The bridge site must have sev-eral possible centerlines with adequate roadnetworks from the unit’s staging areas.Individual centerlines are spaced greater

7-14 Crossing Sites

FM 90-13/MCWP 3-17.1

Current

30 m

30 m 30 m

30 m

30 m

30 m

30 m

30 m

Figure 7–13. Bridge-crossing site

than 300 meters apart to reduce the effect ofenemy artillery and air attacks.

Any method can be used to mark the routeto the bridge as long as markers are visibleto the operators of the vehicles and aremasked to observation from above. As thevehicle approaches the bridge’s edge, mark-ers are spaced 30 meters apart to assistoperators in visualizing the required vehicleinterval on the bridge.

NIGHT OPERATIONS

At night and during limited visibility, bridgecompany soldiers guide the vehicles acrossthe bridge to prevent them from drivingover its side and to help them to maintainthe correct crossing speed.

WARNINGSoldiers must not ground guide vehi-cles by walking in front of them.Instead, soldiers should be placed asguides in stationary positions at rea-sonable intervals along the bridge.

Guides carry flashlights or chemical lightsto guide the vehicles. The first guidemomentarily stops the vehicle at the rampand guides it onto the bridge. He thenshields the lights with his body and stepsout of the roadway. The second guide,spaced about 30 meters farther along thebridge, unshields his lights and directs thevehicle to his location. When the vehicleoperator sees a guide shield his lights, helooks further down the bridge to pick up thenext lights and is guided to them. When thevehicle reaches the guide, he shields hislights and steps aside so that the nextguide can pick up the direction of the vehi-cle. This procedure is continued across thebridge.

ACTIONS UNDER FIRE

If the unit comes under fire while on thebridge, those vehicles that are on it continuemoving to the other side and leave the area.Vehicles that are not yet on the bridge stopand go into a herringbone formation or takeup concealed positions. Once all vehicleshave cleared the bridge, the bridge crew will

Crossing Sites 7-15

FM 90-13/MCWP 3-17.1

break it into rafts and disperse them toreduce their vulnerability to incoming fire.

VEHICLE RECOVERY

If a vehicle breaks down on the bridge, thebridge crew will immediately attach a winch

cable from the far side and drag the vehicleoff the bridge. The recovery vehicle will notmove onto the bridge and tow the disabledvehicle off since the critical requirement isto clear the bridge and maintain traffic flow;loss of the vehicle is far less important.

OTHER GAP-CROSSING EQUIPMENTThe AVLB allows the maneuver force to con-duct a hasty short-gap crossing withoutrequiring bridging assets from the corps.The AVLB allows vehicles up to 70 tons tocross over a 15-meter gap. During thelaunch, the AVLB presents a high profilethat will reveal the breaching location. Thebridge can be launched on the near shoreand then recovered on the far shore andused again. Additionally, the AVLB can beoverlaid on an understrength bridge allow-ing heavy tracked vehicles to cross. In suchinstances, the AVLB must be cribbed toavoid damage to the bridge. The AVLB canbe placed on a stream bottom to assist vehi-cles fording over soft or rocky material, butcaution must be used not to cause severedamage or bottom suction, rendering thebridge unrecoverable.

Overlapping several bridges and interlock-ing them can allow vehicles to ford rivers ofgreater width, but this works best when theonly limiting factor is the depth of the river.In the near future, the AVLB will bereplaced by the Wolverine, which can pro-vide a 24-meter gap-crossing capability forMLC 70 vehicles. It will be transported,launched, and retrieved by an Abrams chas-sis with the turret removed.

The primary role of the MGB, a hand-erectable, heavy-duty bridge, is for tacticalbridging in the forward main battle area. Thekey advantage of the MGB over other fixedbridges is its speed and ease of erection andlittle, if any, site preparation. During assem-bly, soldiers will be vulnerable to small-armsfire, indirect artillery fire, direct weapons

fire, and a nuclear, biological, chemical(NBC) environment. As the situation permitsand the enemy threat is reduced, the MGBwould replace the AVLB to allow greater traf-fic across the gap. Eventually, the MGBwould be removed to be relocated forwardand replaced by other standard or nonstand-ard bridging.

As the danger from enemy action lessens,engineers use the more slowly assembledLOC bridges to augment and then replacethe tactical bridges. The primary use of theBailey bridge is a temporary LOC bridge.It can be used in forward areas to replaceassault bridging and the MGB. This bridgesystem can also be assembled as a railwaybridge, thus providing a relatively rapidrepair capability. In some cases, the Baileybridge is the only tactical bridge suitablefor long spans and heavy loads because itcan be assembled in multiple heights andwidths. Currently, there are large opera-tional stocks of the Bailey bridge inEurope, but there are no plans for addi-tional procurement. Many allied nationshave fielded the Compact 200 Panel Bridgethat is similar to the Bailey but usesadvanced alloys which give it greaterstrength.

Enemy bridges captured by the lead bri-gades are a bonus and speed the crossing.Engineers with the lead brigades neutral-ize explosive devices and reinforce weak ordamaged bridge structures. Commandersrarely base the success of an operationsolely on the seizure of intact bridges andshould not incorporate it in a site-crossing

7-16 Crossing Sites

FM 90-13/MCWP 3-17.1

plan. Targeting of such bridges for direct orindirect fire is relatively simple as bothsides know the locations. In many cases, theload classification of civilian bridges is not

enough for heavy vehicles such as tanks. Ifused in defensive or retrograde crossings,civilian bridges should supplement othercrossing techniques.

Crossing Sites 7-17

FM 90-13/MCWP 3-17.1

CHAPTER 8

Assault CrossingGENERAL

An assault across a river normally beginswith an attack to secure terrain on the exitbank. This may involve an air assault, butthe bridgehead force normally conducts anassault by using pneumatic boats or byswimming amphibious vehicles.

The assault force normally crosses in waves,as sufficient boats are seldom available tocarry the entire force across at once. It is avery complex operation, requiring synchro-nization and skilled application of technicalprocedures. Success requires training andextensive rehearsal.

Forces normally conduct an assault at nightor during limited visibility due to the vul-nerability of forces in small boats on openwater. If an assault must be conducted dur-ing daylight, the assault site must be iso-lated by fires and smoke to reduce theforce’s vulnerability.

This chapter describes an assault-boatcrossing. It focuses on conducting the cross-ing at night. It defines the organizationalelements required to conduct an assaultacross a river and the necessary supportingtechniques and procedures (see Figure 8-1).

TYPES OF ASSAULT CROSSINGSEach lead battalion in a ground assaultshould have at least one ford or assault-boat

site big enough to accommodate two compa-nies abreast.

Assault Crossing 8-1

1. Engineers conduct far-shore reconnaissance.2. Assault and support forces conduct nearshorereconnaissance.3. The assault force conducts a rehearsal (day).4. The assault force conducts a rehearsal (night).5. The assault force moves into the AA.6. The company guides link up with the engineerboat platoons.7. The engineer boat platoons move into the attackposition.8. The support force moves into support-by-firepositions.9. The engineer boat platoons distribute and pre-pare the boats.10. The company guides bring the assault force tothe attack position.11. The boat teams man the boats.12. The preparation teams prepare the far shore.

13. The boat groups carry the boats to the river andlaunch the boats.14. The company flotillas cross the river.15. The support force provides suppressive fires, ifrequired.16. The assault force places smoke on the river, ifrequired.17. The assault force debarks, deploys, andattacks.18. The second-wave force moves to the river.19. The boat groups return to the near shore.20. The engineers mount the motors, if required.21. The second-wave force and cargo are loadedinto the boats.22. The second-wave force crosses the river.23. The far-shore aid station is established.24. The assault force seizes the objectives.25. The assault force establishes the hastydefense.

Figure 8-1. Assault steps, summarized

FM 90-13/MCWP 3-17.1

Fording vehicles are more likely to be usedin a hasty crossing than in a deliberatecrossing because they allow the force to con-tinue across the river without pausing toacquire other crossing means. A ford siteshould have 300 meters along the near bankat the entry point for deploying the supportforce.

RUBBER-BOAT CROSSING

The following factors should be consideredwhen using rubber boats in a crossing. Rub-ber boats—

• Offer great opportunity for surprise in asilent-paddle crossing.

• Are a relatively fast means of crossing,especially when using outboard motors.

• Maneuver well in the water.

• Require limited, if any, entry-bank prep-aration—none is required on the exitbank.

• Require the separation of mechanizedtroops from their vehicles and equip-ment.

• Have limited carrying capacity, particu-larly AT weapons.

• Provide limited protection, mobility, fire-power, and communications on the exitbank.

The unit protects itself during a rubber-boatcrossing by moving silently, during periodsof limited visibility, and crossing at a loca-tion where the enemy does not expect acrossing attempt.

Generally, an infantry platoon uses threerubber boats for its personnel and attachedelements. If short of boats, the dismountedelements of an infantry platoon equippedwith the M2 Bradley vehicle can fit in twoboats. Allocating one squad per boat, whenpossible, preserves unit integrity.

For an assault using rubber boats, each com-pany requires at least 200 meters along theriver to disperse the boats and ideally 300meters between companies. This is a total of700 meters for a battalion assaulting withtwo companies abreast.

Control is very important, particularly atnight when boats can easily become sepa-rated or lose their direction. Combat experi-ence has demonstrated that engineer andinfantry boat rehearsals before the crossingattempt are mandatory for success. Therehearsals should begin as soon as the unitreceives the WO without waiting for thedetailed crossing plan.

AIR-ASSAULT CROSSING

The following should be considered whenusing air-assault asset in a crossing. Air-assault assets—

• Require indirect approaches to avoiddetection.

• Provide the element of surprise.

• Give greater flexibility to emplace per-sonnel and equipment.

• Provide the rapid insertion of forces tothe area where the enemy is located, if aLZ is available.

• Are greatly affected by weather condi-tions.

• Must be a high AD priority at the river,requiring suppression of enemy ADeffort.

• Require the separation of mechanizedtroops from their vehicles and equipment.

• Are vulnerable to armored counterat-tacks and require a quick ground linkup.

Planning and execution are the same as forother air-assault operations (see FM 90-4).As with assault boats, rehearsals are neces-sary, particularly for troops not familiarwith air-assault operations.

8-2 Assault Crossing

FM 90-13/MCWP 3-17.1

VEHICLE-SWIM CROSSING

Against little or no resistance, swimmingthe fighting vehicles may be practical in theassault stage. Swimming the fighting vehi-cles—

• Has minimal effect on troop organizationand control.

• Provides troop protection, mobility, andfirepower on the far bank.

• Provides early AT capability on the farbank by vehicle-mounted tube-launched,optically tracked, wire-guided (TOW)missiles.

• Reduces the number of vehicles to berafted.

• Is a slow operation.

• Is considered risky because the vehiclesmaneuver poorly in the water and areextremely vulnerable to antiarmorweapons.

• Requires suitable entry and exit points.

• Requires vehicle preparation.

• Requires training in vehicle-swim opera-tions.

Rapid reinforcement of dismounted assaulttroops with armored vehicles is so criticalthat it justifies using any expeditiousmethod when swimming the first few fight-ing vehicles across. This includes winching,towing, or pushing the first ones across nor-mally unsuitable places while engineersprepare better entry and exit points for therest.

The space required to swim vehicles on lineis 200 meters of front per company with 300meters between companies. Less is requiredif they cross in a column. Commanders planentry and exit sites to account for down-stream drift when swimming the fightingvehicles.

ORGANIZATIONThe specific organization used depends onMETT-T factors, particularly the size of thebridgehead, the distance to exit-bank objec-tives, and the nature of the enemy’s defense.Regardless of these factors, the assault bat-talion’s TF organizes into support andassault forces and are assisted in theassault by other brigade units in support-by-fire positions.

SUPPORT FORCE

Each assault company has a support forceunder its control. This force covertly estab-lishes a support-by-fire position along thefriendly bank before the assault. It usesnight vision and thermal sights to locateenemy positions. It also develops a fireplan to engage these positions and to pro-vide suppressive fires on all suspected posi-tions. When directed to engage, thesupport force destroys all known and sus-pected positions. The support force must

be positioned early enough to develop adetailed fire plan. The assault-force com-mander directs the support-force com-mander to lift or shift suppressive fires asnecessary.

The support force normally consists of thetanks and infantry fighting vehicles of thedismounted infantry conducting theassault. If an attached light infantry bat-talion is conducting the assault, tripod-mounted heavy machine guns and AT mis-sile systems (augmented by infantry fight-ing vehicles and tanks) provide supportingfires. The company XO controls thesedirect-fire weapon systems; however, thecompany commander gives the firing com-mands.

Supporting artillery battalions and mortarplatoons provide indirect-fire support. Theassault force has priority of fires from at


FM 90-13/MCWP 3-17.1

least one artillery battalion during theassault. The artillery battalion does not nor-mally fire a preparatory fire mission forcovert assaults. The assault force assigns thebatteries priority targets that they fire onupon request. This normally occurs after theinitial wave is ashore or upon discovery. Ifthe assault is not covert, the battalion firespreparatory fires that continue during thecrossing of the first wave, lifting on com-mand when the boats approach the exitbank.

Graphic fire-control measures are essentialbecause of the danger of firing on friendlyforces. Boundaries between companiesshould run along terrain features that areeasily visible in the dark to help control indi-rect fire during the dismounted assault.Counterbattery fire is imperative to thesuccess of the river crossing. The target-acquisition-battery-radar team deploys tocover the area before the assault crossingbegins.

Smoke may not be used to support the firstwave of a covert crossing because of the riskof losing surprise but should be used to hidelater waves as they cross. If the crossing isopposed, a smoke haze should cover the firstwave before it enters the water to reducedirect-fire effectiveness. The assault-forcecommander initiates smoke obscuration. Ifsmoke generators are available, they aredeployed to obscure a large length of theriver. Additional smoke along multiple siteson the river conceals the true crossing area.This additional smoke may be from smokepots if nothing else is available.

If units must fire smoke onto the far shoreto cover the crossing area, they fire it onthe command of the assault-force com-mander after surprise is lost. Mortars arethe primary means of indirect-fire smoke.Direct-support artillery is generallyreserved for supporting fires.

AD teams deploy along the near shore of theriver to cover the crossing. Once in place,they remain until the brigade releases them.They can move across the river and link upwith the assault force only after otherSHORAD systems have taken position tocover the river. The crossing sites remain thepriority AD area throughout the crossing.

ASSAULT FORCE

The first assault wave moves the bulk of thedismounted force across covertly. This forceattempts to provide sufficient security onthe far shore so that the second and laterassault waves can cross after surprise islost. The first assault wave carries—

• Rifle platoons.

• Attached assault engineers.

• Forward observers.

• The command group.

The organization of the first wave permitsrapid deployment of the force into a tacti-cal formation on the far shore. Individualboatloads retain unit integrity at the low-est level. The two basic boatload configura-tions are the rifle-squad boat and the rifle-platoon-headquarters boat (see Figure 8-2).

Each boat contains an engineer boat crewand a rifle squad. The squad boat also car-ries an engineer assault team, while theplatoon boat carries the platoon headquar-ters. The boat-force commander is thesenior occupant. He commands the forceup to the attack position and after itdebarks on the far shore. The coxswain isthe "pilot in command" and commands theforce from the point that it mans the boatin the attack position until it debarks onthe far shore.

First-wave boats carry only critical cargo,such as AT weapons, machine-gun ammuni-tion, demolitions, and engineer tools thatare required for reducing obstacles.


FM 90-13/MCWP 3-17.1

Bow gunner

Riflesquad

Strokepaddler(engineer)

AssaultengineerteamSquad leader(compass)

Boatcommander

Coxswain (engineer) Occupied boat position

Vacant boat positionSquad boat

Boatcommander

Platoon boat

Coxswain (engineer)

Riflesquad

Bow gunner

(platoon leader)

FO

RTO

Medic

Strokepaddler(engineer)

Squad leader(compass)

Figure 8-2. Boat-load configurations

Platoon boats form a boat group of threeboats that are spaced 20 meters apart onthe water. The boat group forms into a "V,"with the platoon leader's boat acting as theguide boat in the center. The two engineerassault teams are from an engineer squad,with a squad leader commanding the teamin the right boat and an assistant squadleader commanding the team in the leftboat. The assault teams re-form into asquad upon debarking.

Platoon boat groups form into company flo-tillas (see Figure 8-3, page 8-6). The com-pany commander commands the guide boatin the center platoon. The company com-mand group disperses between boats, fill-ing in vacant boat positions. Platoon guideboats maintain a 40-meter interval (two-boat interval) between boat groups.

The first wave of the assault may consist ofthree company flotillas crossing on line.Battalions do not have a prescribed crossingformation. Each company crosses in its ownzone and attacks it own objectives.

All undamaged boats return to the nearshore after carrying the first wave. Thesenior coxswain of the group will consolidatethe boats and stroke paddlers into one (ormore) boat and daisy-chain the other boats tothe lead boat to expedite the time requiredfor the boats to return to the near shore. Thesecond and later waves carry across theremaining troops and materials that are nec-essary to seize the far-shore objective.

The second wave carries company aid sta-tions and may include the battalion com-mand group. Since sufficient AD systems


FM 90-13/MCWP 3-17.1

20 meters 40 meters

Figure 8-3. Company flotilla

are in place to cover the crossing area, thebrigade may release some or all of the bat-talion AD teams to cross in the secondwave.

The second wave also transports additionalmaterial and ammunition that is notrequired for the initial assault but neces-sary to establish a defense. This mayinclude antiarmor weapons, mortars,ammunition, laser designators, mines, orpioneer tools. It normally includes tripod-mounted weapons, such as M2HB .50-caliber machine guns, TOW AT systems,Mark 19 40-millimeter grenade launchers,and the ground-laser location designator(GLLD).

If secrecy is not required for the secondwave because the first wave is in combat, orif the enemy has begun to fire on the cross-ing area, then outboard engines are used topropel the boats so that paddlers are notnecessary.

The immediate movement of some heavyAT weapons across to support the dis-mounted assault battalion is essential. Thisis critical enough to justify extraordinary

actions. As vehicles carry all heavy ATweapons, engineers concentrate on forcinga few critical vehicles carrying heavy weap-ons across immediately after the secondwave. They hand carry heavy weapons, ifnecessary, even before direct fire andobserved indirect fire has been removedfrom the crossing area. Vehicles cross byswimming or fording or are dragged orrafted across.

CAEs begin bank preparations on both thenear and far shore, using hand tools andequipment where possible. They swim anM9 ACE or deep ford a bulldozer to get awinch capability to the far shore. Bradleyvehicles either swim or ford, with towingassistance if necessary. A BEB can towBradleys if the current’s velocity is toohigh. Using a block and tackle fastened toa tree or picket holdfast, a BEB can helpBradleys leave the water over unpreparedbanks. If high-mobility multiwheeled vehi-cle (HMMWV) weapon carriers are avail-able, they can be waterproofed and pulledacross on the bottom with a winch cable. Ifabsolutely necessary, rafting can be used,but this risks destroying equipment thatwill be critical later in the crossing.


FM 90-13/MCWP 3-17.1

ENGINEERS

Engineers supporting the assault areattached to the assault unit as described inprevious paragraphs. Each assault com-pany receives an engineer platoon thataccompanies the assault force to its objec-tive, helping it fight through obstacles andprepared defenses. The engineers help theassault force establish hasty defenses afterit has seized its objectives. Engineers nor-mally come from the division engineer bat-talion that supports the brigade.

Boat engineers—

• Operate the boats and cross the assaultforce.

• Are in direct support of the assault bat-talion until it has secured its objectives.

• Remain on the water after the assaultforce has crossed and continue to carrymen and materials across in assaultboats until heavy rafts can take over themission.

• Improve exit and entrance banks forrafts and boats and assist with crossingthe initial heavy weapons.

• Come from the engineer battalion thatwill remain on the river operating thecrossing area.

Two boat engineers are assigned to eachassault boat. They are the coxswain and thelead paddler on the right side of the boat(stroke paddler). The stroke paddler controlsthe stroke cadence during the assault cross-ing. The boat engineers paddle the boatsback for the next wave. Outboard motors nor-mally are used during the second wave.

Normally, an engineer platoon must operatethe boats for a first-wave assault company.An engineer company can cross the assaultbattalion of a brigade. Each assault companyrequires 9 boats plus a safety boat. Theassault battalion requires 30 boats to carrythe assault companies plus 1 for the battal-ion commander. If less are available, somecompanies may not cross in the first wave.

PREPARATION PHASE OF THE OPERATIONSimilar to conducting a deliberate breach ofa complex obstacle, river-crossing opera-tions require intelligence collection, detailedplanning, and preparation. These must allbe synchronized to allow the force to main-tain its momentum and surprise thedefender at the point of penetration.

FAR-SHORE RECONNAISSANCE

Tactical reconnaissance of the far shoremust cover a broad front to a significantdepth to determine the details of the ter-rain and the enemy's defenses. Thisshould occur early and cover sufficient ter-rain to disguise the actual crossing area.

Engineers conduct a technical reconnais-sance of the far shore, focusing on theimmediate crossing area. An engineer lightdiving team conducts a reconnaissance at

night. If a diving team is unavailable, thena swimming reconnaissance team is madeup from the engineer unit supporting thecrossing. Strong swimmers (Red Cross-certified lifeguards or water-safety instruc-tors) from the engineers supporting thecrossing make up the reconnaissanceparty if divers are not available. Two swim-mers make up a reconnaissance team toscout a company crossing area.

The reconnaissance team carries heavilylubricated weapons and wears LBE. Theywear subdued face masks and runningshoes and use swimming fins. Divers mustwear Class 5 life jackets as flotationdevices (US Army flat foam-filled life jack-ets will not serve). The divers camouflagetheir faces and hands and tow any neces-sary equipment in bundles.


FM 90-13/MCWP 3-17.1

Divers must carefully avoid splashing. Ifnecessary, they wear weights to ensurethat kick strokes are underwater. Theparty enters the water far upstream fromthe actual crossing site and floats with thecurrent while crossing. Divers use the side-stroke, facing each other and observingbehind the other diver. This allows 360-degree observation and communication byhand and arm signals. When the diversapproach the shore, they switch to thebreaststroke so that they can observe thelanding area. Divers must use stealth andcaution when approaching the beach. Theymust keep a low profile in the water andalso on the beach.

When the divers reach shallow enoughwater and determine that the situation issafe for landing, they remove their fins. Ifthey can immediately enter the woods uponleaving the water, they do so in a rush. Ifthe woods are a distance from the water,one diver remains in the water just at thewaterline and covers the other as he movesquickly across the beach. Once the inlanddiver has reached the edge of the woods, hecovers his partner, who is moving acrossthe beach to the same position.

Critical information requirements include—

• The characteristics of the bank atassault-boat landing areas.

• The depth of the water to a distance of4.6 meters off shore.

• Any obstacles along the shore.

• The locations of enemy observationposts.

The reconnaissance team checks potentialareas identified from the near shore andevaluates each based on its ability to supportassault boats and disembark troops. Thereconnaissance party also checks areas

where raft and bridge centerlines can beinstalled.

Far-shore reconnaissance is conducted earlyand at multiple sites along the shore to gen-erate information necessary for planning andselecting the most suitable areas. Maneuverunits, with support from the engineers, con-duct far-shore reconnaissance.

FAR-SHORE PREPARATION

The far shore is prepared immediatelybefore the assault crossing. The prepara-tion team consists of a two-man reconnais-sance team and a two-man cargo teamwith an inflatable reconnaissance boat;both teams are from the supporting engi-neers. The reconnaissance team that con-ducted the far-shore reconnaissance isnormally best-suited to do the far-shorepreparation. The preparation teaminstalls landing markers for the flotillas. Aseparate team normally marks each com-pany zone to speed up preparation.

The reconnaissance team and the cargoteam are equipped the same as the recon-naissance party and use the same tech-niques. The reconnaissance team crossesfirst, floating downstream to the landingsite with the current. Upon landing, theymove to the correct landing site for theassault landing and signal for the cargoteam to cross. The reconnaissance teaminstalls transit lights to guide the cargoteam as it crosses.

Signaling is accomplished by sending aprearranged Morse Code letter using aflashlight equipped with an opaque filter.The transit lights consist of either twoflashlights with opaque filters and direc-tional cones or two chemical lights in theirfoil wrappers with small areas torn opento release light. The team installs thelights so that one is about 1 meter abovethe water and the other is about 2 meters


FM 90-13/MCWP 3-17.1

above the water and 2 meters behind it,facing 45 degrees upstream.

The cargo team waits until signaled tocross. It uses a three-man reconnaissanceboat as a flotation device to carry markingmaterials, mine detectors, night-vision gog-gles, and a radio. The reconnaissance boatis covered with a camouflage net section andis partially deflated after loading so that itfloats low in the water to reduce its signa-ture. The camouflage net is secured to thelifelines to aid in holding the cargo in thepartially submerged boat. The cargo teamcrosses oriented on and swimming slightlyupstream of the transit lights so that it candrift into the shore with the current, limit-ing the noise and the splash.

The preparation team installs landingmarkers as its first priority. These are thesame types of markers used to guide thecargo team. They must be adequately visibleto the assault force but dim enough not toharm night vision. If flashlights are avail-able, they have opaque and/or colored filtersinstalled to limit the light output. Chemicallights remain in the foil wrappers with onlyenough foil removed to provide the neces-sary light. All landing markers are transitlights that mark the position and help theboats set the proper course relative to the

current. Normally, if the current is less than0.5 MPS, the lights are set perpendicular tothe river. If the current exceeds 0.5 MPS,the lights are set at a 45-degree angle to theriver, facing upstream. Double transit lightsmark the center boat group’s landing area,and single transit lights mark the flankgroup’s. If colored lights are available, greenlights mark the right boat group’s landingarea, white the center’s, and red the left’s(see Figure 8-4).

The preparation team also makes a finalexamination of the landing areas formines or obstacles. If it discovers isolatedmines, it marks them and the routesaround them. If the team finds a majorminefield that will significantly hinder thelanding at a site, it either notifies theassault force and moves the site upstreamor downstream to avoid the mines orattempts to reduce the minefield. Once thepreparation is complete, the team signalsthe assault force to begin crossing, initiat-ing the movement of the first wave carry-ing the boats from the attack position. Thepreparation team then finds cover near thelanding area for the center boat of a predes-ignated boat group (generally the centerboat group) and awaits its arrival. This boatgroup is especially alert for linkup with thepreparation team. While waiting, the team


GGGGGRRRRREEEEEEEEEENNNNNWWWWWHHHHHIIIIITTTTTEEEEERRRRREEEEEDDDDD

Leftboatgroup

Centerboatgroup

Rightboatgroup

Figure 8-4. Landing marker lights

Leftboatgroup

Centerboatgroup

Rightboatgroup

FM 90-13/MCWP 3-17.1

continues to watch for enemy activity andalerts the assault force of any significantchanges.

NEARSHORE RECONNAISSANCE

Units must be extremely careful to hidereconnaissance elements conducting near-shore reconnaissance in the crossing area orto deceive the enemy about what they aredoing.

Battalion and company command groupsmust conduct a daylight reconnaissance ofthe crossing area. They must see theembarkation and debarkation points andkey landmarks to help guide the forcewhen crossing. They must also see theattack position and the routes from it tothe river. Company guides must walk theroutes from the dismount points to theboat-group positions within the company’sattack position. Engineer boat coxswainsmust see the routes they will traversefrom the attack position to the water.

Support-force leaders and vehicle command-ers must covertly select firing positions andlocate concealed routes into the positionsfor their vehicles during daylight. Theyshould identify sectors of fire and conductextensive observation within the sectors toacquire specific targets.

ASSAULT-FORCE REHEARSAL

An assault-boat crossing cannot be con-ducted effectively in the face of oppositionwithout thorough rehearsal. If possible, theforce should conduct two rehearsals. Oneshould be during daylight to learn the pro-cedures, and one should be at night underactual assault conditions.

The rehearsal area should be similar to theactual crossing area but away from theriver to preserve secrecy. Generally, a rear-area river is the rehearsal area.

Before rehearsal, the boat crews and infan-try train together in the actual boat teamsassigned for the crossing. Soldiers receivetheir boat assignments and practice intheir assigned positions until the boatscan move effectively on the water. Thetraining must include carrying and launch-ing the boat, embarking, watermanship,emergency actions, debarking, and hasty-defense preparations.

NOTE: After the rehearsal, boat assign-ments must not be changed.

During training, the coxswain forms theboat team. He forms the crew members ina column of twos in the relative positionsthat they will occupy in the boat, with pas-sengers at the rear of the two columns. Hethen numbers the crew. The right-side pad-dlers are 1, 3, 5, and 7, and the left-sidepaddlers are 2, 4, 6, and 8 (both sides frombow to stern). The stroke paddler is alwaysnumber 1, and the coxswain is alwaysnumber 15, regardless of the number ofpaddlers used. Passengers are numberedconsecutively from bow to stern startingwith number 11, who is always the bowgunner. The coxswain addresses all crewmembers by number. When the coxswainwishes to address a command to a pair ofpaddlers, he uses their numbers together,as in "1 and 2" and "3 and 4."

Figure 8-5 shows only 8 paddlers. The boatcan carry 15 soldiers. If fully loaded, theboat requires 10 paddlers. Boat-positionnumbers do not change.

All forces participating in the assaultcrossing rehearse together. The supportforce moves into position, and the assaultforce crosses in the same waves it will usefor the actual crossing. The rehearsalshould cover the AA through to the seizureof the assault-force objectives.


FM 90-13/MCWP 3-17.1

Bow gunner

Strokepaddler

Paddlers

Coxswain

Paddlers

13 5 7 9

11 12 13 14 15

24 6 8 10

Figure 8-5. Boat numbering

EXECUTION PHASE OF THE OPERATIONThe objective of an assault river crossing isto project combat firepower to the exit bankwithout being detected by the enemy or,once detected, project it at a faster rate thanthe enemy can concentrate forces for a coun-terattack. The use of air assets is desired;however, there are normally not enoughassets available, or the risk of beingdetected is to great. To maintain momentumand allow maximum combat power acrossquickly, the maneuver force negotiates theriver on a broad front. Detailed planningand specific responsibilities allow units tocross and quickly establish a tactical foot-hold on the far side to—

• Prevent the enemy from indirect-fireobservation.

• Allow rafting and bridging operations tobegin.

ATTACK-POSITION PROCEDURES

The attack positions must be large enoughto accept a dismounted infantry rifle com-pany. They should—

• Be accessible to trucks or carrying par-ties bringing the assault boats.

• Be concealed from hostile ground andaerial observation.

• Be connected with clearly defined footroutes to the river.

• Be within 100 to 200 meters of the river.

• Be in defilade from hostile flat-trajectoryfire.

Trucks carry assault boats and life jacketsas far forward as possible without compro-mising secrecy. They are met at the desig-nated unload position by the engineerplatoon and company guides from eachattack position, who will unload the truckand carry the boats into place. The platooncan carry two at a time, so this will requirefive trips. If possible, HMMWVs moving at alow speed to minimize noise can carry sev-eral boats at a time into the attack position.

Within the attack position, boat crews dis-perse assault boats and life jackets along


FM 90-13/MCWP 3-17.1

the boat-group routes to the river. Thesafety boat is positioned as the last boat inthe downstream boat group. The remaininglife jackets for passengers and the coxswainare arrayed behind the boat.

After the boats are prepared, each engineersquad provides a guide to bring each pla-toon from its AA to the nearshore crossingsite. The platoon leader sends the guideparty to the AA, where each guide links upwith his boat group. The remaining engi-neers establish local security around theattack position and await the boat groups.

Soldiers arrive in the attack position withtheir weapons cocked on an empty chamber,selector switch on SAFE, and magazinesremoved. Squad leaders must verify this inthe AA before moving to the attack position.The soldiers are organized, without the boatengineers, into boat teams and boat groupsin the AA. They travel as boat groups. Whenthey arrive at the attack position, theirguide leads them directly to their boats.

When the boat team arrives at its boat, thecoxswain commands, "Crew, boat stations."Each team member takes his proper boatposition, with passengers lining up to therear. The coxswain then directs the team toload and check weapons. The team insertsthe rifles' magazines and verifies that theyare seated. However, the team does notchamber the rounds. All weapons remain onSAFE. Squad leaders verify that all weap-ons are on SAFE. The coxswain then directsthe team members to sling their weaponsand don their life jackets. Paddlers slingtheir rifles diagonally so that the barrelextends up over the shoulder which will beaway from the boat when standing alongsideand facing forward. Odd-numbered paddlerssling their rifles over their right shoulder,even numbered over their left. This allowscarrying the boat at high carry and reducesinterference with paddling. Muzzles must be

up during all boat operations to preventpunctures. The teams then await the com-mand to proceed to the water.

EMBARKING PROCEDURES

On order of the company commander, thepaddlers of the boat crew carry the boats tothe river. They make no unnecessary stopsfrom the time of departure from the attackposition until the boat reaches the bank.The coxswain directs either "Low carry" or"High carry." In low carry, crew memberslift the boat to about knee height, by thecarrying handles while facing forward, andcarry the boat at arms length. In high carry,crew members lift the boat to about headheight, place it on their inboard shoulders,and carry it while gripping the carryinghandles with their outboard hands. Nor-mally, high carry is used for long distances,and the boat is shifted to low carry whenapproaching the bank. Paddles remain inthe boat during carry procedures. Remain-ing crew members follow the boat to thewater.

The boat crew may launch the boat eitherbow first or stern first; however, bow first isthe preferred method. The boat islaunched—

• Bow first whenever the water is shallowenough for the team to wade in carryingthe boat at low carry.

• Stern first when the water is too deep forwading or when the launch point hassteeply sloped banks.

Bow-First Method

On the coxswain's command, "Launchboat," team members perform a low carryand move into the water at a fast walk.When the depth of the water is such thatthe boat floats free of the bottom, allhands continue pushing it into the river,remaining at their relative positions along-side the boat.


FM 90-13/MCWP 3-17.1

As the water reaches the knees of the firstpair of paddlers, the coxswain commands,"One and two in." The first pair of pad-dlers climb into the boat, unstow their pad-dles, and give way together. The coxswainorders each pair of paddlers into the boatin succession by commanding, "Three andfour in," "Five and six in," and "Seven andeight in." The pairs climb into the boat oncommand, break out their paddles, andpick up the stroke of the stroke paddler.

The coxswain orders the passengers into theboat after the paddlers by commanding,"Eleven in," "Twelve in," and so forth. Pas-sengers board over the stern and move for-ward in the boat to their positions. Thecoxswain enters the boat last and soundsoff, "Coxswain in, hold water."

Stern-First Method

On the coxswain's command, "Launch boat,"team members perform a low carry andcarry the boat stern (rear) first to thewater's edge. They launch the boat by pass-ing it back along the line of team members.When the stroke paddler can no longer helppass the boat back, he moves to the bow ofthe boat and handles the towing bridle.Other team members follow suit, takingtheir places along the towing bridle betweenthe stroke paddler and the boat.

When the boat is in the water, the coxswainenters the boat and takes his station. Heorders the boat team to load, starting withthe rearmost left-hand paddler, by com-manding "Eight in," "Seven in," "Six in,""Five in," "Four in," "Three in," and "Twoin." Passengers embark next as he com-mands, "Fourteen in" and "Eleven in." Whenthe coxswain is ready to cast off, he allowsthe boat to drift back and turns it to faceacross the river.

If motors are to be mounted before thefirst-wave crossing, the coxswain brings

the boat in to shore stern first after theboat is manned and holds it in place eitherby a line to shore or by holding bottom.Two engineers wade to the boat carryingits motor and mount it on the transom.

TACTICAL CONTROL AFLOAT

The coxswain navigates the boat and directsthe paddlers. He controls the movement ofthe boat in the water as well as embarka-tion and debarkation from it. He ensuresthat the guide boat maintains the properstation. The boat commander sits in front ofthe coxswain and directs the boat in anemergency. He also commands the boatoccupants upon landing until the unit hasre-formed. The boat commander directsfires from the boat, if necessary.

Each platoon has a platoon guide boat,which contains the platoon headquarters.Other platoon boats position themselves toeither side of the platoon guide boat aswingmen to maintain a 20-meter intervalfor protection against fires and to allowdispersion on landing. They follow theguide boat and land when it does. Theyopen fire from the boat when the guideboat does.

Each company has a C2 boat, which carriesthe company commander and leads his flo-tilla. Platoon guide boats position them-selves at double-boat intervals from the C2

boat, maintaining a 40-meter spacingbetween boat groups. The C2 boat is nor-mally the lead boat of the center platoon.

The battalion command group remains on thenear shore until the assault wave has landed.The commander controls the nearshore directfires and directs changes in landing points ifelements of the first wave encounter difficul-ties. He also directs changes for the followingwave. The commander has his own boatand crosses on his own schedule, but henormally crosses with the second wave.


FM 90-13/MCWP 3-17.1

The command group normally does notcross in a single boat but is distributedamong several boats.

Guide boats in all boat groups are responsi-ble for ensuring that their group lands atthe proper place. Landing marker lights areinstalled as transit lights to assist naviga-tion on the water. The coxswain will see twolights, one above the other. If the boat ismoving straight to the landing, the lightswill be straight in vertical alignment. Ifnot, the lower light points in the directionthe boat must go to be exactly headed forthe landing. The boat will not head directlyfor the transit lights except when the riverhas no current. The boat heads for the farshore so that the boat's true course isdirectly for the lights (see Figure 8-6).

Normally, the boats will cross slightlyupstream from the landing so that they can

drift in with the current. To do this, theyalign so that the lower transit light pointsslightly upstream.

If the force is conducting a crossing wheresmoke is necessary on the water and itobscures the far shore, other navigationmethods it could use include stringing ferrylines across the river for the boats to follow,using floating markers, or traveling on acompass heading.

WATERMANSHIP

Watermanship includes all the skills thatthe boat crew must exhibit to properly con-trol its boat in the water. It includes individ-ual paddling skills, responsiveness tocommands, and the skill of the coxswain.

Individual paddlers use a paddling tech-nique where they push the paddle verticallyinto the water, roughly 1 meter to theirfront, and then power it back through thewater by pushing with the upper hand whileusing the lower (guide) hand for control. Atthe end of the power stroke, they remove thepaddle from the water, turn it outboard andparallel with the water's surface (feather-ing), and move it forward for the nextstroke. The stroke is silent, with the pad-dlers careful not to strike the side of theboat or to splash.

The stroke paddler sets the pace to controlthe paddlers. He receives oral commandsfrom the coxswain and establishes andmaintains the paddling pace. All paddlersmatch the stroke of the paddler in front ofthem except for the number two man, whomatches his stroke with the stroke pad-dler. If the boat crew has difficulty pad-dling in unison, the coxswain can exerciseoral control by calling cadence. The nor-mal paddling speed is 10 strokes perminute for stealth and 30 strokes perminute for speed.

TTTTTrrrrr aaaaannnnn sssssiiiii tttttlllll iiiii ggggg hhhhh ttttt sssss

Boatheading

Current

Actual movement direction

8-6

Figure 8-6. Boat course

Boatheading

Actualmovementdirection

Current


FM 90-13/MCWP 3-17.1

The coxswain uses the following commandsto control the boat:

• "Hold water." Paddlers hold their pad-dles motionless in the water with theblade perpendicular to the direction ofmotion.

• "Give way together." Paddlers stroke inunison following the rhythm set by thestroke paddler.

• "Slow stroke." The stroke paddler pad-dles 10 strokes per minute.

• "Fast stroke." The stroke paddler pad-dles 30 strokes per minute.

• "Backwater." Paddlers paddle backwardin unison with the stroke paddler.

• "Rest paddles." Paddlers rest their pad-dles across their legs.

• "Hold bottom." Paddlers thrust theirpaddles straight down into the river’sbottom and hold them against the side ofthe boat as a temporary anchor.

• "Land boat." The stroke increases to 30strokes per minute, with each paddlerdigging deep into the water for power todrive the boat up on shore. The strokepaddler stows his paddle as soon as theboat grounds, then disembarks andsecures the towing bridle to the shore.

• "Right, backwater, left, give waytogether." When paddlers execute thesecommands, the boat turns rapidly to theright. When the boat has turned to thenew desired course, the coxswain com-mands, "All, give way together."

• "Left, backwater, right, give waytogether." When paddlers execute thesecommands, the boat turns rapidly to theleft. When the boat has turned to thenew desired course, the coxswain com-mands, "All, give way together."

The coxswain can make minor adjust-ments in the boat's speed by directing,"Slow the stroke" or "Speed the stroke."

The coxswain must take the current’svelocity into account when trying to hold acourse. In low-velocity current, the boatcan travel a relatively straight courseacross the river by crabbing slightlyupstream. To do this, the coxswain aimsthe bow of the boat slightly upstreamwhile sighting on the land mark. If themark remains on a constant bearing (itdoes not drift upstream or downstream),the boat is crabbing correctly and isheaded directly for the landing.

If the current's velocity is too high for suc-cessful crabbing (over 0.5 MPS), either theboat must start upstream or the coxswainmust steer a figure-eight pattern. In bothcases, the boat should approach the land-ing heading into the current to avoid thedanger of broaching. If the boat islaunched from far upstream, it generallyfollows a course similar to the dottedcourse in Figure 8-7, page 8-16. If the cox-swain follows a figure-eight course, hesteers upstream until aligned with thetransit lights, then lets the bow drop down-stream and guides by using the lightsuntil he reaches the landing point. Hethen steers upstream to the landing marks(see Figure 8-7, solid line). These tech-niques minimize the amount of time theboat will be traveling slowly against thecurrent while near the enemy shore.

The need for a figure-eight course is deter-mined during reconnaissance. The flotillacommand boat sets the figure-eight course,completing the downstream turn in align-ment with the transit lights. Remainingboats simply maintain station until thelast turn upstream toward the landingarea. Boat groups then head directly forthe transit lights.


FM 90-13/MCWP 3-17.1

Currenth

FFFFFaaaaarrrrrssssshhhhooooorrrrreeeee

TTTTTrrrrr aaaaannnnnsssssiiiii tttttlllll iiiii ggggghhhhhtttttsssss

Figure 8-7. Figure-eight course

Current

Eddy currents (eddies) occur at channelbends, near points of land, and at placeswhere the bottom is uneven. Eddies can bedangerous to small boats. The coxswainmust be alert for them.

OBSCURING WITH SMOKE

The purpose of smoking the crossing site isto achieve a haze over the water that canrender direct and indirect fires less effec-tive. Smoke may be used during river-crossing operations to—

• Conceal the movement of the initialassault force.

• Isolate the exit bank of the river forrapid occupation by maneuver forces.

• Conceal emplacement of crossing means,such as engineer bridges.

During river-crossing operations, smokemay be used for—

• Obscuration

• Screening.

• Marking.

• Deception.

It is particularly important not to produce acolumn of smoke above the water that canpinpoint the crossing location. For this rea-son, smoke is not used if conditions will nothold it close to the surface.

Smoke production depends on wind direc-tion. If the wind is blowing from the nearshore toward the far shore, smoke genera-tors or support-force vehicles can effectivelysmoke the crossing. If the wind tends toblow parallel to the river, nearshore smokeshould not be used, as it will make a smokewall that will silhouette boats on the river.In this case, floating smoke pots anchoredacross the width of the river can produce


FM 90-13/MCWP 3-17.1

effective smoke. If the wind is blowing fromthe far shore to the near shore, smoke potsor mortar smoke on the far shore can beeffective.

DIRECT-FIRE REACTION

If the boat is subjected to heavy direct firewhile crossing, the boat commander maydirect all personnel, except the bow gunner,to stow their paddles, slip over the sidewhile holding the safety line, and propelthe boat to shore by kicking with their feet.

All boats have a designated gunner at thebow that is armed with either a squadautomatic weapon (SAW) or a bipod-mounted machine gun. The gunners do notfire unless the boat commander ordersthem to. If ordered to fire, the gunnersengage the most dangerous target or sup-press the landing area. More often, thegunners engage enemy weapons firing onthe assault force by firing back up the lineof enemy tracers. If two passengers areavailable to be boat gunners, the secondback from the bow should be armed with agrenade launcher.

To preserve their night vision, all paddlersobserve the paddle of the man to theirfront. They do not look at the enemy shorefrom where the muzzle flashes are coming.

INDIRECT-FIRE REACTION

If the boat is subjected to heavy artilleryfire while crossing and the boat commanderdirects, the coxswain turns the boat down-stream and propels it at a fast stroke withthe current out of the artillery impact area.If the boat is equipped with a motor, it isstarted and the paddlers stow their paddlesand maintain a low posture.

DEBARKING PROCEDURES

The manner in which the coxswain ordersthe boat team to land the boat depends onthe depth of the water at the landing point.

Shallow Water

As the boat nears the landing point, the cox-swain directs the boat toward the landingand orders, "Land boat." As the boatgrounds, paddlers stow paddles and disem-bark over the side into the water. They thenhold the boat for the passengers to disem-bark. The stroke paddler secures the boatand awaits to return it.

Deep Water

As the boat comes along the shore, the cox-swain orders, "Stroke out." The stroke pad-dler stows his paddle and, with towingbridle in hand, gets out of the boat onto theshore. He then pulls the boat up close to theshore and secures it if he can. Otherwise,crew members will have difficulty debark-ing. The other crew members stow theirpaddles. The coxswain then directs debark-ing by number, beginning with the passen-gers, then the shoreside paddlers, andfinally the riverside paddlers. The coxswainis the last to leave the boat. He and thestroke paddler secure the boat and await toreturn it.

Immediately upon leaving the boat, the boatteam forms a hasty perimeter. The bow gun-ner moves directly forward, roughly 10meters, and drops prone, observing to hisfront. The left-side squad members move upand form a prone semicircle to his left. Thesquad leader takes charge of his squad anddirects all soldiers to drop their life jackets.He then awaits orders from his platoonleader.

BOAT RETURN

As soon as the boat team has formed a hastyperimeter and dropped their life jackets, thestroke paddler recovers them and returnsthem to the boat.

The boat engineer squad leader (the seniorengineer with the boat group) takes chargeof all three boats in the boat group. He


FM 90-13/MCWP 3-17.1

supervises the tying off of all three boats ina trail and loads all six engineers into thefront boat. They then paddle the boat backto the friendly shore, towing the other twoboats (see Figure 8-8).

On the return, the boat group travels in arelatively straight line to gain distance fromthe enemy shore as rapidly as possible. Thiswill cause the group to drift downstream.Upon reaching the near shore, the boatgroup turns upstream and travels closeinshore until it reaches its original depar-ture point (see Figure 8-9). A guide from theengineer platoon headquarters guides themin for the next wave.

If the boats have outboard motors, all threeboat crews start their motors on commandof the boat engineer squad leader andreturn independently to the near shore.

MOTOR PROCEDURES

If motors are available, they speed thecrossing significantly. Normally, the firstwave uses paddles to cross covertly. Afterthe boats return from carrying the firstwave, the motors are mounted. If the boatscan be placed in the water without enemyobservation (in a lagoon or barge basin, forexample), the motors are mounted on theboats before the first wave crosses. In this

situation, the motors can be started imme-diately if the crossing is discovered. Themotors are also available for returning theboats after the first wave.

If a covert crossing cannot be achieved, thefirst wave may cross the river powered bymotors. In this case, the motor is mountedbefore the boat crew and passengers carrythe boat to the shore. Two additional engi-neers are provided to help carry the stern ofthe boat to the shore. The crew paddles theboat while the coxswain starts the motor inorder to reduce exposure time on the river.This technique must be practiced during therehearsal.

If time permits or the distance to the wateris great, the two-man team of engineersfrom the crossing-area engineer battalioncarries the motor to the water and mounts iton the boat. The boat is manned and heldwith the bow toward the river and the sternto the shore. If the bottom is shallow, thepaddlers hold bottom. If the water is toodeep or the current too strong, a line is fas-tened to the boat stern to hold it against theshore. The mounting team wades out toplace the motor on the stern and fastens itin place. The coxswain directs the paddlersto give way together after the motor ismounted. He then starts the motor with the


Figure 8-8. Boat return

FM 90-13/MCWP 3-17.1

Figure 8-9. Operation of boat group

Guide

Current

Enemy

boat under way. If the boat has too few occu-pants to move effectively by paddles (duringthe second wave, for example), the boatremains at the shore until the coxswainstarts the motor.

Preparation is critical for success with out-board motors. The primary problem is hardstarting. All motors are started and run upto operating temperature during prepara-tion. If any are difficult to start, replace-ment motors are substituted (the hard-starting motors become backups). Aftermechanical checks and warm-ups, the fueltanks are completely filled with the correctfuel and oil mixture to eliminate condensa-tion. In cool or cold weather, the motors arekept warm until needed, using a warmingtent, ambulances with medical markingscovered, a heated building, sealed wrapping,or other means.

CARGO PROCEDURES

Porters detailed from the assault force bringthe cargo forward. They carry it to the

waterline at the boat launch point to awaitthe return of the boats. When the boatsreturn, the porters load and secure the cargoto the boat. If the cargo includes heavy orpointed items, a temporary plywood floor isplaced in the boat before loading.

Porters accompany the cargo to the farshore to unload it. The cargo is unloadedinto caches until carrying parties are sentback from the assault force to get them.

CASUALTY PROCEDURES

Platoon medics accompany assault forces inthe first wave. They carry their medicalbags and night-vision goggles but do nothave litters. They treat wounded wherethey fall, sending walking wounded back tothe landing area and leaving more severelywounded where they were treated.

The second wave carries senior aidmen withequipment to establish a far-shore casualtycollection point in each company zone. Theaid station should provide a blackout shelter,


FM 90-13/MCWP 3-17.1

such as a tarpaulin or small tent, for patientexamination along with emergency medicalsupplies and quantities of intravenous fluids.The second wave also carries litter teamsformed from the headquarters elements ofthe assault force. The litter teams carry

wounded back to the collection point. Thesenior aidman at the collection point per-forms triage and treats patients. Prioritypatients are evacuated by assault boats asthey become available. All other patientswait until rafts are available.

SAFETYSafety is as important in combat as it is inpeacetime training. Procedures are estab-lished and soldiers are trained in peacetimeto be safe in combat. Loss of a soldier to anaccident in combat is just as intolerable aslosing a soldier in peacetime and is poten-tially far more dangerous to the force.Safety procedures are particularly impor-tant when considering the risks duringassault river crossings, where the lost sol-dier may be the key to mission success.Therefore, all safety procedures must be fol-lowed in combat.

The most important safety procedure isbuilding a well-trained force. Nothing is agreater safety risk than allowing a force ofuntrained soldiers to undertake a complex,potentially hazardous task where the well-being of all depends on each soldier knowinghis job. Peacetime training should never beavoided because of the potential hazards ofa necessary combat task. Training to stan-dard in a controlled environment is the onlyway to surmount the hazards and build con-fidence in the soldiers' ability to accomplishtheir mission.

Life jackets are always worn when usingassault boats. If Class 5 life jackets (German-army style) are available, they are wornover LBE and the diagonally slung rifle.The Class 5 life jacket will support a soldierso equipped and hold his head out of thewater. If a life jacket providing lesser flota-tion is used, such as the standard US Armyflat foam-filled life jacket, it is worn overthe uniform. The LBE is worn over the lifejacket, with the belt unfastened and the

rifle slung diagonally over all. Rifle slingsare turned around so that the free end isalways away from the weapon. This allowsrapid jettison of the rifle in the water bypulling the free end of the sling to releasethe fastener.

Weapons are always carried in the boatswith the bolt forward on an empty chamberand the weapon on SAFE. The only excep-tion to this is the bow gunner, who willcharge his weapon in the boat whendirected to fire. He must put the weapon onSAFE before debarking, and the squadleader must verify this by touch. The soldiercan immediately engage the enemy, uponlanding, by simply taking the weapon offSAFE and charging the chamber.

WARNINGThe soldier must NOT take theweapon off SAFE and charge thechamber before leaving the boat.

A safety boat is always used during anassault crossing. One safety boat is used forevery company flotilla. It contains at leastone lifeguard-qualified swimmer (two, ifpossible) to assist soldiers that may fall intothe water. This lifeguard will not wear bootsor LBE. The safety boat will also contain aboat hook and a float with an attached linefor rescuing troops in the water. Rocket-propelled lifelines will be included, if avail-able. At a minimum, the boat commander isequipped with night-vision goggles. Thecrew of the safety boat comes from the sup-porting engineer force that provides theboats and boat crews and consists of eight


FM 90-13/MCWP 3-17.1

paddlers, the coxswain/commander, a medic,and one or more lifeguards. The crew shouldalso have a radio tuned to the company'sfrequency.

The safety boat crosses parallel with a flotillaand about 40 meters downstream. Its crewpays out a climbing rope fastened to the nearshore as a safety rope and attaches life jack-ets as floats every four boat lengths (see Fig-ure 8-10). When the crew reaches the enemyshore, it ties off the safety rope and thenmoves back to the center of the river. If a mangoes in the water or a boat capsizes, theaffected boat group makes a quick radio callon the company’s frequency, indicating thenumber in the water and the boat group call-ing. The alerted safety boat holds water

while its crew looks for troops who are in thewater or who are caught by the safety rope.

If a soldier goes in the water, he shouldimmediately remove his helmet andrelease it. He should then roll onto hisback. If he is wearing a Class 5 life jacket,he retains his rifle and LBE. If he is wear-ing a lesser-quality life jacket, he releaseshis rifle and LBE and drops them. He thenallows the current to carry or float him tothe friendly shore. He stays alert for thesafety rope and safety boat. If he reachesthe safety rope, he wraps his arms in it orclips a snap link to it on his LBE (if he iswearing LBE). He either waits for thesafety boat or moves along the rope to thenearest shore.

F l o a t

Figure 8-10. Safety boat and guard rope

Float


FM 90-13/MCWP 3-17.1

CHAPTER 9

Engineer OperationsGENERAL

A river crossing requires specific proceduresfor success because the water obstacleinhibits ground maneuver in the usual way.It demands detailed planning and differenttechnical support than other tactical opera-tions. Extensive use of corps engineer assetsare required. It is critical for supportingcorps engineers to be totally involved in allfacets of the river-crossing operation frominitial planning through preparation andexecution.

Traffic control is the most vital componentof a river-crossing operation. ERPs are usedto control traffic flow and permit movement

across the river to be unhindered. Engineerunits provide positive control and the neces-sary equipment to ensure maneuver forcessuccessfully and safely cross the river in atimely and synchronized manner.

Contingency operations may require thatassault river-crossing assets be used forlonger periods of time because fixed bridg-ing is not feasible or readily available. Engi-neer units must implement techniques thatallow the long-term use of assault bridgingassets without heavily affecting operationsor damaging equipment. These topics willbe discussed in detail in this chapter.

ERP OPERATIONSERPs ensure the effective use of the cross-ing means. ERPs and TCPs may be colo-cated to provide control for the rivercrossing. The CSC uses them to rapidlyorganize and move the unit through thecrossing area.

The CSC establishes ERPs at the call-forward area and, if enough engineerassets are available, at the staging areaand the far-shore holding area. He usesadditional ERPs only when specific siteconditions make it necessary for crossing-area control. ERP personnel need suffi-cient space to mark an area the size of araft (mock-up raft), brief crossing proce-dures, and conduct necessary inspectionsand rehearsals. A hardstand, such as arest stop or parking lot, is ideal for thispurpose but lacks the overhead conceal-ment usually desired. Some ERP functionsmay be done at separate ERPs to ensure a

smooth and rapid flow of vehicles to theriver. In this case, it is essential to main-tain communications between ERPs.

Typically, an engineer squad mans an ERP.This maintains unit integrity and providessufficient personnel and equipment for con-tinuous operations. The crossing-site head-quarters establishes direct communicationwith ERP personnel to control raft-load orindividual vehicle movement. Depending onthe location and purpose of the ERP, it canbe used for the following functions:

• Briefing crossing-unit personnel on pro-cedures, including safety.

• Demonstrating ground-guide signals.

• Inspecting equipment to ensure that itmeets the load-class capability of thecrossing means.

• Organizing vehicles into raft loads.

Engineer Operations 9-1

FM 90-13/MCWP 3-17.1

• Conducting rehearsals.

• Controlling vehicle movement.

RAFTING OPERATIONS

ERP personnel configure vehicles into raftloads and send them to the river to coincidewith the arrival of an empty raft. Engineersbrief crossing units before their arrival inthe call-forward area to make this happenas rapidly as possible. The briefing coversthe—

• Route and its markings through thecrossing site.

• Road speed and interval.

• Loading and unloading of rafts.

• Location of passengers while raftingacross the river.

• Configuration of the vehicles for thecrossing.

• Actions to take for disabled vehicles andthe location of the maintenance collec-tion point.

• Hand and arm signals and signalingdevices.

• Arm bands or other identification ofguides and traffic controllers.

• Issuing, wearing, and returning of lifejackets.

• Location of holding areas and alternateroutes.

• Location of the casualty collection point.

• Actions to take in the call-forward area.

• Actions to take in case of enemy fire.

• Regrouping of the company in the far-shore holding area.

An engineer from the squad running theERP can brief vehicle crews and rehearsethe movement signals with them. The

staging area is an ideal place to do this,minimizing the time and effort spent orga-nizing a crossing unit in the call-forwardarea. Otherwise, a separate ERP shouldhandle this task.

Figure 9-1 is an example of an ERP at thecall-forward area. The engineer squad leaderpositions himself where he can best controlvehicle movement from the call-forward areato the river line. He establishes communica-tion with the crossing-site headquarters. Asa crossing unit arrives, the assistant squadleader contacts the unit’s commander, whodetermines the order in which his vehicleswill cross. The assistant squad leader thenconfigures individual vehicles into raftloads, while ensuring that the vehicles do notexceed either the weight limit or the maxi-mum dimensions of the raft. He has a spacemarked out in the exact dimensions of a raft(mock-up raft) for this purpose. An engineersquad member guides the vehicles onto thismockup raft, using the same procedure to beused at the raft’s embarking point on theriver. At the same time, another engineerinspects the vehicles for the proper load clas-sification and dimensional clearances andchalks the raft-load number on the vehicles.Once cleared through the mock-up, an engi-neer squad leader releases individual raftloads to the river as directed by the crossing-site headquarters.

Items useful for running an ERP couldinclude—

• A TA1 field phone and an RL39 withwire.

• Two rolls of engineer tape and six stakes.

• Ten traffic markers.

• Flashlights with colored filters.

• Chemical lights.

• Signal flags.

9-2 Engineer Operations

FM 90-13/MCWP 3-17.1

9-1

Rafting operations

One raft load Mock-upraft

Engineer tape

NCO establishesraft loads

Squad leader

Ready lane

Traffic markers

Traffic controlinformation

Call-forward area

Traffic-controlinformationCall-forward area

Figure 9-1. ERP layout

• Chalk.

• Camouflage nets and poles.

• Night-vision goggles.

• Sandbags.

BRIDGE OPERATIONS

A bridge operation requires a continuoustraffic flow to the river. Units must bebriefed and sent to the crossing site quickly.

To accomplish this, engineers brief at stag-ing areas and check vehicle load classifica-tion and dimensional clearances. Thebriefings include the following rules:

• Vehicles will maintain a maximum speedof 9 kph while crossing the bridge.

• Vehicles must not stop on the bridge.

• Operators must not shift or make abruptchanges in speed on the bridge.


FM 90-13/MCWP 3-17.1

• Vehicles will maintain the interval indi-cated by signs on the side of the road.

• Operators will follow the signals of engi-neers at ramps and intervals along thebridge.

ERPs may be established along the routesto the crossing site to regulate traffic. Amockup bridge is not necessary at the ERP.

SWIMMING OPERATIONSFor swimming operations, ERP personnelhave the necessary briefings and vehicle

inspections. Crossing units are responsiblefor most preparations, but ERP personnelcan assist with operations at the predipsite that is established nearby and providerecovery assets. A briefing on swimmingoperations should include—

• The layout of entrance and exit markers.

• Swamping drills.

• Rescue procedures.

• The actions to take in case of enemy fire.

ENGINEER CONTINGENCY BRIDGING OPERATIONSOrganizing and training for war fightingremains the primary mission of Army engi-neers. However, engineers can be called onto conduct contingency operations. Forexample, US Army operations in Bosniaincluded the mission to bridge the SavaRiver near Zupanja, Croatia, in December1995. This mission was the largest river-crossing operation since World War II andwas conducted under extreme conditions.Seasonal weather caused the Sava river toswell from its normal width of 300 metersto more than 600 meters. Despite harsh con-ditions, engineers used Chinook helicoptersto deploy ribbon-bridge sections into theriver while other engineers rebuilt theapproaches and successfully bridged theSava river to allow elements of the 1stArmored Division to cross. As the floodwa-ter receded, engineers built a causewayacross the floodplain. As operations in thearea continued, the ribbon bridge remainedthe only crossing means for both militaryand civilian traffic while preparations weremade for fixed bridging.

Versatile engineers provide unique per-sonnel and equipment capabilities thatcan effectively support complex and sensi-tive situations in any contingency opera-tion. Therefore, engineer force-projection

planning should include the possibilitythat forces committed to contingency opera-tions may become involved with combatoperations. The engineer commander tai-lors engineer support based on contingency-operation requirements, which may beradically different than supporting com-bat operations. In many cases, the onlydifference between a wartime and an engi-neer contingency operation is the threatlevel.

Contingency operations may require thesame or a greater level of logistics support toengineers as wartime operations. Combat-ant commanders tailor logistics support toengineers based on theater needs. Logisticsefforts are integrated with host-nation orlocal resources and activities. Engineersinvariably get involved with a wide varietyof gap-crossing operations that may needflexible logistics support. Critical engineerlogistics considerations during contingencyoperations include—

• The availability of construction equip-ment.

• A direct-support maintenance capability.

• Repair-parts supply.

• Class IV construction materials.


FM 90-13/MCWP 3-17.1

ASSAULT BRIDGES, LONG-TERM USE

Ribbon-bridge operations normally last nolonger than 72 hours. Having the ribbonbridge remain in operation beyond that timeframe presents problems for the engineersthat normally would not be experienced dur-ing a short duration. Equipment mainte-nance, anchorage systems, constant changesin the water level, and repair of approachesmust be considered for long-term use ofassault bridges.

MAINTENANCE

As equipment remains in use during cross-ing operations, maintenance servicesbecome more difficult to manage. Timemust be made to allow boats and bays tobe recovered from the water and com-pletely serviced and checked for unusualwear. The techniques discussed in Chapter7 are applicable but must include completerecovery of the equipment and movementback to the EEP where the services can bedone. To accomplish maintenance serviceswithout jeopardizing bridging operations,boats and their replacements must be care-fully managed. This may require procur-ing more boats than authorized by thetable(s) of organization and equipment(TOE) to permit continued crossing opera-tions without distribution for maintenance.

To check and service interior and end baysof the ribbon bridge, it must be brokenapart and replacement interior and endbays emplaced. Time for such actionsshould be incorporated into the bridge-crossing time line and maneuver units noti-fied when the crossing site will be shutdowntemporarily. Synchronization of alternatingtimes for crossing sites to be closed for main-tenance can proactively re-route traffic flowand prevent major disturbances in move-ment across the river. To expedite the timerequired to replace bays needing mainte-nance and quickly allow traffic to resumecrossing operations, engineers prepare

replacement bays and boats and stage thembefore closing the crossing site. Daily checksof the bridge throughout the operation, con-siderations of the current's velocity and theamount of debris that may affect thebridge's operation, and maintaining vehiclespeed across the bridge are critical to pre-vent damage to the bay's lower-lock devicesand roadway-to-bow portion latches.

ANCHORAGE

All military bridges must be held in positionby some anchorage system. Short-termanchorage is normally used for assaultbridges, but if the bridge is required toremain operational for a longer period, theanchorage must be upgraded to providelong-term support.

The design of any anchorage system is influ-enced by several factors, including the—

• Width of the river.

• Current's velocity.

• Depth and bottom conditions of the river.

• Height and slope of riverbanks.

• Conditions of the soil.

• Depth of the groundwater table.

• Availability of equipment.

Anchorage of the ribbon bridge must occur ifthe bridge is used for long-term operation.During short-term crossings, boats maintainthe bridge's stability against the current'svelocity and keep the bridge from being dam-aged. However, as time permits, an anchor-age system must be emplaced to providecontinuous stability and provide relief for thenumber of boats required. Initially, theanchorage may consist of a combination ofshore guys and boats. This method can stillallow the bridge to be broken and permitbarge river traffic access. Eventually, a semi-permanent anchorage system, such as an


FM 90-13/MCWP 3-17.1

overhead cable system, should be emplacedto keep the bridge secure.

The three basic components of all long-termanchorage systems include approach guys,an upstream anchorage system, and a down-stream anchorage system. Approach guys arecables that prevent the bridge from beingpushed away from the shore as a result of theimpact of vehicles driving onto the ramps ofthe bridge. The upstream anchorage systemholds the bridge in position against the forceof the current's velocity. The downstreamanchorage system protects the floatingbridge against reverse currents, tidal condi-tions, eddies, and high winds or storms thatmight temporarily alter or reverse the natu-ral flow of the river. The following types ofanchorage systems can be used for stabilizinga bridge:

Kedge Anchors

Kedge anchors lie in the streambed and aresecured to the bridge bays with anchorlines. They are designed to sink with thestock lying flat and the fluke positioned todig into the bottom. On hard bottoms, thekedge anchor is useless.

Shore Guys

Shore guys are cables attached from thebridges to a deadman or similar holdfastson the shore. Shore guys can be upstream ordownstream provided that the maximumanticipated current (or reverse current fordownstream systems) does not exceed 0.9MPS. Shore guys can be used for any lengthof floating bridge provided that a 45-degreeangle be maintained between the shore guyand the bridge centerline.

Combination of Kedge Anchorsand Shore Guy

A combination system may be used forupstream or downstream anchorage systemsin currents less than or equal to 1.5 MPS.When constructing a combination system,

attach kedge anchors to every float and ashore guy to every sixth float.

Overhead Cable

An overhead cable system consists of one ormore tower-supported cables spanning theriver parallel to the bridge. Each end of theoverhead cable is secured to the shore, pref-erably through the use of a deadman. Bridlelines are used to connect each bay of thebridge to the overhead cable. The cable func-tions like a cable used in a suspensionbridge, except that its final working positionis inclined toward the bridge because of theforce of the current on the bridge.

TC 5-210 provides the specific criteria forthe design of an overhead-cable anchoragesystem, to include the cable design, towerdesign and placement, and deadmandesign.

PROTECTIVE SYSTEMS

Floating bridges, particularly those that willremain in place for long periods of time,must be protected against severe weatherconditions and enemy destruction. If floodconditions or heavy debris hamper bridgingoperations, removing of interior bays willreduce the lateral pressure on the bridgeand allow the debris to pass downstream. Iflosing the bridge is imminent, release anend section and securely anchor the bridgeparallel to the shore until conditions permitresuming bridging operations. As the river'swidth increases, simply add more interiorbays to the bridge to compensate.

The enemy may attempt to destroy floatingbridges in a variety of ways, including airattacks, land attacks, underwater demoli-tions teams, floating mines, or assaultboats. It is necessary to construct floatingprotective devices to prevent waterborneforces from damaging or destroying thebridge. The three types of floating protectivesystems are as follows:


FM 90-13/MCWP 3-17.1

Antimine Boom

This device is designed to stop any minesthat are sent downstream toward the bridge.The antimine boom is placed far upstream toprotect the other protective devices as well asthe bridge. It consists of a number of logs orother large floating structures attached to acable running across the river. Concertina isnormally placed along the length of the boom.

NOTE: Before using timber logs or rail-road ties, ensure that they are notwaterlogged and will float.

Impact Boom

The impact boom is designed to withstandthe impact of large natural or man-madedebris and stop the enemy from attackingthe bridge by boat. It is constructed by plac-ing a series of floats and cables across theriver. The cables absorb the impact of thedebris or boat and restrain it until it can beremoved or destroyed.

Antiswimmer Net

This net is used to stop swimmers or under-water demolition teams from reaching thebridge. The net can be constructed by sus-pending a mesh or net barrier from ananchorage cable to the river’s bottom. Con-certina may also be connected to the cableand net to prevent swimmers from climbingover the net. The net must be firmly affixedto the river's bottom or enemy divers can eas-ily go under the net. The antiswimmer netshould also be placed on the downstream sideof the bridge to prevent enemy divers fromreaching the bridge from downstream.

Army diver teams can assist in emplacingthe protective devices and test them toensure they are able to prevent penetratingthe bridge.

APPROACHES

Over a period of time, traffic flow at thesame location will eventually wear the

approaches down and make them unusable.Engineers incorporate repair of the entryand exit banks and the approaches lead-ing to the crossing site into the crossing-operation plan. Initially, the approachesmay be suitable to receive heavy trafficwith little effect, but implementation ofreinforcing the approaches must be donefor long-term traffic. When inspectingapproaches, consider the following:

• The steepness of the approaches.

• The ruts or gullies along the approaches,particularly in a floodplain area.

• Water-level conditions and expectedchanges due to weather or seasonal con-ditions.

• The location of alternate approaches(alternate crossing sites) to allow for therepair of existing approaches.

Matting and rock or gravel are the bestsuitable materials to use to support theapproaches. Maneuver units that will haveto conduct long-term crossing operationsshould develop procedures to requisitionand deliver these materials to identifiedcrossing-site locations. Reconnaissanceteams can locate local quarries where rockand gravel can be obtained through coordi-nation with the host country.

New techniques for constructing bridgeapproach roads include using fabric as areinforcement across soft soil. An impervi-ous, neoprene-coated, nylon-woven mem-brane can be placed between a stoneaggregate and the soft-surface soil to allowthe ground to withstand heavy traffic. Themost important feature that a reinforcingfabric membrane can offer is improving soilstability and strength, which createssmaller deformations from vehicle trafficthan soils acting alone.


FM 90-13/MCWP 3-17.1

LONG-TERM GAP-CROSSING C2

More than any other mobility task, gapcrossing involves managing combat power,space, time, and terrain. The controllingheadquarters must be flexible enough toreact to any changes in the tactical situationand scheme of crossing. This is particularlydifficult when involved with long-term oper-ations in the same area of operations. Man-agement of the crossing site, enemyconsiderations, traffic-control measures,and CSS must be synchronized for long-term activities and must not be based onless than a 72-hour period.

Management

Traffic and movement control remain theresponsibility of the C2 headquarters. Activ-ities may direct that another unit take overthe crossing operation and equipment as awhole or bring their own crossing equip-ment and personnel to relieve the existingunits and permit them to move forward. Allaspects of the operation must be coveredwhen handing over the crossing site to thegaining unit—just as though they were con-ducting the crossing for the first time.

Enemy Considerations

Operation of a single crossing site over anextended period of time increases the possi-bility of enemy interdiction. The possible useof nuclear or chemical weapons againstfriendly crossing activities impacts on controlprocedures. To prevent the friendly elementsfrom becoming targets, forces must cross thegap as swiftly as possible to minimize theconcentration of forces on either side of thegap. The controlling headquarters also variesthe crossing-site location to reduce enemythreat interdiction.

Traffic- Control Measures

Staging- and holding-area control must bemaintained. These areas must be located farenough away from the gap to facilitatererouting and the use of alternate roads tocrossing sites. Staging and holding areas onthe far shore must be developed to handlethe traffic as vehicles travel back across.New routes may be constructed and existingroutes upgraded to improve traffic flow.Staging areas must be able to provide thefollowing:

• Cover and concealment.

• A sufficient area for vehicle and equip-ment dispersion.

• Easy accessibility.

• Sufficient trafficability to prevent delayscaused by increased traffic flow withinthe area of operation.

Combat Service Support

In a normal gap-crossing situation, the com-mitted combat forces will be temporarilyseparated from their full CSS. For long-termgap-crossing operations, increased trafficflow for the service-support vehicles must beconsidered and controlled. Sufficient cross-ing sites and designated crossing times canensure that priority is given to field trainsand ensure that timely resupply operationsare not hindered. Recovery of nonmission-capable equipment presents an additionalproblem for recovery teams transporting theequipment back to the near shore for direct-support maintenance support. Additionally,recovery resources should continue to beprovided at both sides of the crossing sitesso they can quickly recover a vehicle unableto cross and prevent delays.

MULTIROLE BRIDGE COMPANY (MRBC)Today’s Army must be able to respond to anincreasing array of potential employmentsin war or in contingency operations. With

the new integrated information-processingsystems, river-crossing opportunities will bequickly identified and execution will rely


FM 90-13/MCWP 3-17.1

heavily on the rapid-response capability ofbridge companies.

Current bridge companies are tailoredaround their specific floating or fixed-spanbridges, without regard for their inherentconceptual, operational, and organizationalcommonalty. Both types of companies aresimilarly organized with a company head-quarters, two bridge platoons, and a supportplatoon. The fixed-bridge company cannottransport ribbon-bridge sections on its 5-tondump trucks, nor does it have the requiredbridge boats. The float-bridge company, onthe other hand, can readily transport fixed-bridge components on its transporters, butonly if the loads are palletized.

Whenever both types of bridges are needed,both types of companies must deploy. Sincea company owns it own unique bridge, suffi-cient companies must be deployed to coverall possible gaps. When a bridge companyhas expended its bridging materials, itreverts to a transportation mission.

The MRBC is a modular company with bothdry- and wet-gap capabilities that willemploy both types of bridges as needed,based on METT-T. Each bridge platoon cantransport and employ both types, asordered. The MRBC is a versatile, flexible,and modular unit that can meet thedemands of the maneuver commanders. Thedevelopmental HDSB is also fully compati-ble with the MRBC concept. The HDSB willreplace the MGB as the primary fixedbridge employed by this company, relegatingthe MGB to a supplemental role.

ORGANIZATION

The MRBC will be a combination of a MGBcompany and an AFB company. The MRBC’sstructure consists of a company headquar-ters, two bridge platoons (one MGB and oneAFB), and a support platoon. The supportplatoon consists of a platoon headquarters,

an equipment maintenance section, and abridge-site section. The new bridge trans-porter, the improved common bridge trans-porter (ICBT), is specifically designed tofunction in the MRBC. The palletized-load-system (PLS) trailer will be procured as apart of the HDSB to allow the transportingof both bridges simultaneously.

BASIC CONCEPT

A typical operational mission would beginwith a platoon responding to a missionwith an initial basic load of the desiredbridge. When it completes the bridge, theplatoon moves to the next site, either pick-ing up the next required bridge along theway or finding the bridge cached at eitherthe engineer bridge park or the site it willbe emplaced. As the forces advance, thebridges become the responsibility of theengineer units in the communicationszone. As prefabricated bridging is replacedby nonstandard or more permanent bridg-ing, the platoon responds to bridge-retrieval missions. Retrieved bridges willreenter the supply system or be stored inthe unit’s bridge supply yard. Bridgingsets are a supply commodity and are han-dled as any other Class VII supplies(major end item).

The MRBC’s capabilities will give com-manders the ability to quickly maneuverand respond, through either fixed or floatbridging or a combination of bridgingappropriate for the mission. This newlystructured MRBC operates within a “lane”on the battlefield (an area defined by amaneuver brigade’s area of operation) andprovides the necessary bridging for multi-ple axes of advance. Trailing closelybehind combat forces, the MRBC movesforward when necessary to support assaultcrossings. Additional MRBCs, providedfrom corps assets, may be assigned to thelane when gap-crossing requirementsexceed the capabilities of a single MRBC.


FM 90-13/MCWP 3-17.1

IMPLICATIONS

Because bridge sets are exceptionallyheavy and tall and have many parts (someare small and easy to lose), they should beplaced on pallets and shrink wrapped fortransportability and accountability. Theprocedure to requisition and deliverbridges is essentially unchanged. The num-ber of bridges needed is unaffected, sinceit is based on METT-T and not the bridge-company organization.

Bridges are loaded on bridge adapter pal-lets and boats that have the improved boatcradle, which allows the loads to be placedon the ground without damage. The pal-lets and cradles remain at the EEP untilthe bridge or boat is recovered. Treatingbridging as a commodity instead of abridge company TOE property emphasizesthe critical maneuver planning that isinvolved by the maneuver staff and notexclusively the engineer staff. MRBC engi-neers cannot exist on the battlefield with-out support from the following branches:

• Quartermaster—to order and trackbridge stocks.

• Transportation—to haul replenishmentbridge sets forward to engineer bridgeparks.

• Ordnance—to repair transporters, erec-tion boats, and bridge components.

TRAINING

Engineer units' training must reflect thedual bridge capability. Currently, bridgecrewmen receive advanced individual train-ing on both fixed and float bridges. However,once they are assigned to a unit, their collec-tive training is only on the single-type bridgeof that company. Under the MRBC concept,individual bridge crewmen and leaders mustmaintain their proficiency on both types ofbridges. Bridge specialists must continue tobe proficient in all types of prefabricatedbridges. Critical branch interaction duringwar-gaming exercises must consider employ-ing the MRBC in current training by imple-menting a variety of missions, eithersequentially or simultaneously, to becomemore accustomed to its employment. Addi-tionally, engineer company-grade officers andnoncommissioned officers (NCOs) will haveincreased responsibility and will need toimprove their technical proficiency.

Final decisions as to the size and end-statecomposition of the MRBC are not beingimplemented yet; however, many units canexpect to have the HDSB and the improvedribbon bridge carried on HEMTT-chassistransporters. Interim organizations willinclude basic loads of the medium-girder,Bailey, and ribbon bridges, which are carriedon their current transporters. Whatever theorganization’s development stage, the MRBCwill not be dedicated to only one bridge type.


FM 90-13/MCWP 3-17.1

APPENDIX B

Engineer-Planning CalculationsGENERAL

This appendix addresses the detailed engi-neer planning necessary for a river-crossingoperation. The charts and overlays that areused to synchronize and control execution ofthe crossing are shown in Figures B-1

through B-8 and Tables B-1 through B-4,pages B-4 through B-13. The H, as used inthe figures in this chapter, stands for H-hour; this is the specific hour the assaultphase begins (see FM 101-5-1).

ENGINEER PLANNINGInitial engineer planning at corps and divi-sion levels focuses on providing sufficientengineer assets to handle crossing require-ments. The terrain teams at division andcorps levels maintain the terrain databasethat provides potential crossing sites andriver widths. The division engineer uses thisinformation to construct a site overlay (seeFigure B-1, page B-4). He labels assault andrafting or bridging sites and shows the sitecapacity and the estimated preparationtime for each site (from the terrain data-base).

Preparation time is the time required toimprove routes and riverbanks to supportthe units that will use the site. It alsoincludes the time required to construct raftsand bridges. Rafting-site capacity is thenumber of raft round trips per hour. Theengineer calculates rafting-site capacity bymultiplying the number of raft trips per hourby the number of rafts and the number ofcenterlines at the site (see Table B-1, page B-5). Centerlines must be at least 100 metersapart. Each assault company needs 200meters of river frontage. Figure B-1 showsthe determination of rafts per hour and thecapacity of the assault site for the divisioncrossing overlay. The site overlay providesadditional details necessary to ensure thateach brigade has sufficient potential crossingsites within its boundaries. Table B-2, page

B-5, provides planning factors for assault-boat operations.

Rules of thumb for making this determina-tion follow:

• A brigade requires 31 assault boats tocross a battalion with three companiesin the first wave. With 70 boats, it cancross two battalions at once. Generally,the boats with the corps bridge compa-nies can handle these requirements.

• A brigade requires two bridges or theequivalent bridging configured intorafts.

The engineer planner uses the above rulesof thumb to task-organize engineers thatare supporting each crossing area. The divi-sion engineer then develops a rough cross-ing time line using pure battalions. Thisprovides sufficient information for divisionplanning, without requiring detailed knowl-edge of the brigade’s plan. Table B-3, pageB-5, provides necessary planning factors(field trains are not included). Figure B-2,page B-6, illustrates a crossing time lineusing 6-float rafts.

The brigade headquarters does the major-ity of planning for the detailed crossing.During the mission analysis, the brigadeengineer also develops a crossing time lineto provide initial buildup-rate information

Engineer-Planning Calculations B-1

FM 90-13/MCWP 3-17.1

to the maneuver planners when they outlinepossible schemes of maneuver. This timeline is the same as the time line that isdeveloped at the division and may be pro-vided by the division engineer.

Once the commander identifies the COAs todevelop, the staff engineer develops crossing-area overlays for each (see Figure B-3, pageB-7). These overlays are developed by usinginformation from the site overlay, along withadditional terrain data. The crossing-areaoverlays show staging areas, holding areas,call-forward areas, and routes for each cross-ing site included in the COA. A crossing-area overlay is necessary for each COA.The overlay for the COA eventuallyselected is later modified by adding ERPs,TCPs, and crossing-area-headquarters infor-mation and is used to support the operation.

When maneuver planners develop COAs,they assign crossing sites and the order ofcrossing to units and task-organize the puremaneuver battalions into TFs. The engineeruses this information to construct a crossingtime line for each COA. He calculates thenumber of vehicles and raft loads for eachunit using pure company figures from TableB-4, page B-8. The company’s raft require-ments do not include the field trains. Theengineer then calculates the crossing timefor the unit by using the crossing capacity ofthe site assigned to it. The crossing timeline shows these crossing periods, by site,based on the order of crossing. The engineerthen develops a detailed crossing time linebased on the task organization (see FigureB-4, page B-9).

During the comparison of the COAs, theengineer uses time lines, brigade-site over-lays, and crossing-area overlays to demon-strate the differences in the crossingplans. After the commander has selectedthe COA for the mission, the staff converts

it into a detailed plan. The engineer devel-ops a vehicle-crossing-capability chart.

He starts by displaying the capabilities ofeach crossing site in terms of raft loads perhour (rafting operations) or vehicles perhour (bridging operations). Since the cross-ing rate for rafts is less during darkness,each site shows total raft trips separately(during day and during night). An exampleof the product of this first step is shown inFigure B-5, page B-10).

The engineer determines the crossingrequirements using the factors from TableB-4. He then blocks out the crossing peri-ods for all units based on site assignment,site capability, and the crossing order inthe scheme of maneuver. After adding theunits’ crossing periods to the chart, hecoordinates the plan with the S3 to ensurethat the units will arrive on the far shoreby the times they are needed (see Figure B-6, page B-11). If not, the S3 and engineerwork together to adjust the crossing orderof subordinate units. The basic technicalinformation remains constant as differentcrossing sequences are checked until onemeets far-shore requirements. The vehicle-crossing-capability chart is the primarytool for finalizing the crossing plan.

After the crossing order has been estab-lished, the engineer develops the crossing-synchronization matrix (see Figure B-7,page B-12). This is the tool that the CACand CAE will use to synchronize the execu-tion of the crossing. It is constructed as achart, with the unit’s locations and activi-ties displayed by time on the upper half andterrain occupation displayed by time on thelower half. The staff can follow each unit'slocation as the operation progresses and caneasily see potential conflicts resulting fromchanges. The matrix also provides criticalinformation for traffic control.

B-2 Engineer-Planning Calculations

FM 90-13/MCWP 3-17.1

The crossing synchronization matrix is con-structed backwards by first portraying theunits' crossing times established from thevehicle-crossing-capability chart, then byusing road movement times to show routeusage and staging-area times. The time re-quired for the crossing of the assault force isalso included. Once all of the units are dis-played, the same information is transferredto the lower terrain portion of the matrix.

The staff immediately resolves any conflictsthey discover while preparing the matrix.

The final engineer planning step is develop-ing the engineer execution matrix (see Fig-ure B-8, page B-13). It displays subordinateunits' task assignments by time. It is usefulboth for tracking unit execution and for aid-ing decisions if changes to the plan are re-quired.


FM 90-13/MCWP 3-17.1


Site

Riv

erW

idth

in

Met

ers

Riv

erF

ront

-ag

e

Num

ber

ofR

afts

/C

ente

r-lin

e

Num

ber

ofC

ente

r-lin

es

Raf

t R

ound

Tr

ip/

Hou

r/C

ente

r-lin

e

Tota

l R

aft

Rou

nd

Trip

/H

our

Pre

p T

ime/

Tota

l Raf

t/H

our

117

530

02

35.

432

1-ho

ur p

rep

32 r

afts

/hou

r

Ass

ault

A a

nd 2

180

410

24

5.4

433-

hour

pre

p43

raf

ts/h

our

316

040

02

46

480.

5-ho

ur p

rep

48 r

afts

/hou

r

Ass

ault

B a

nd 4

140

600

16

6.7

401-

hour

pre

p40

raf

ts/h

our

515

025

02

26

241.

5-ho

ur p

rep

24 r

afts

/hou

r

615

031

02

36

362-

hour

pre

p36

raf

ts/h

our

716

530

02

36

360.

5-ho

ur p

rep

36 r

afts

/hou

r

Ass

ault

C15

040

0N

AN

AN

AN

A2

co

815

035

02

36

362-

hour

pre

p36

raf

ts/h

our

Ass

ault

D a

nd 9

160

610

26

672

0-ho

ur p

rep

72 r

afts

/hou

r

1017

037

52

36

360-

hour

pre

p36

raf

ts/h

our

Ass

ault

E17

565

0N

AN

AN

AN

A

1118

030

02

35.

432

1-ho

ur p

rep

32 r

afts

/hou

r

Ass

ault

F17

568

5N

AN

AN

AN

A

1217

025

02

26

241-

hour

pre

p24

raf

ts/h

our

xx

xx

x

NO

TES

:1.

Obt

ain

the

river

'sw

idth

from

the

terr

ain

data

base

and/

orre

conn

aiss

ance

.

2.S

eeTa

ble

B-1

fort

henu

mbe

rofr

aftr

ound

trip

spe

rhou

rper

cent

erlin

ean

dth

enu

mbe

rofr

afts

perc

ente

rline

.3 .

Det

erm

ine

the

amou

ntof

avai

labl

eriv

erfr

onta

gefr

omth

ete

rrai

nda

taba

sean

d/or

rec

Site

1

Site

2 a

nd A

ssau

lt A

S

ite 3

Site

4 a

nd A

ssau

lt B

S

ite 5

S

ite 6

Site

7

Ass

ault

C

S

ite 8

S

ite 9

and

Ass

ault

D

Site

10

A

ssau

lt E

S

ite 1

1

A

ssau

lt F

S

ite 1

2

2 co

3 co

3 co

3 co

3 co

x

Fig

ure

B-1

. D

ivis

ion-

site

ove

rlay

FM 90-13/MCWP 3-17.1


Table B-3. Unit rafting requirements

Units Vehicles

Raft Trips Required

4 Bays 5 Bays 6 Bays

Armored battalion 161 119 101 86

Mechanized battalion 153 112 65 55

FA battalion 165 97 61 52

Engineer battalion (ERI) 139 77 59 50

ACR 208 171 110 98

NOTE: Assume that current velocities are less than 0.9 MPS and that battal-ions/regiments are at 100 percent MTOE strength.

Table B-1. Raft-center line data

River Width in Meters

Round Trip in Minutes

Number of Raft Trips per Hour Number of Rafts

75 7 8.6 1

100 8 7.5 1

125 9 6.7 1

150 10 6.0 2

175 11 5.4 2

225 12 5.0 2

300 16 3.75 3 to 5

NOTE: Planning times are for current velocities up to 1.5 MPS

Table B-2. Boat-planning factors

Equipment Characteristic

River Width

75Meters

150 Meters

300 Meters

Pneumatic assault boat with an OBM

Minutes per round tripTrips per hour

320

415

512

Pneumatic assault boat without an OBM

Minutes per round tripTrips per hour

415

610

106

NOTES:1. Factors are averaged based on load/unload time and safety.2. Planning times are for current velocities up to 1.5 MPS. For faster current veloc-ities, classification must be reduced to a caution or risk crossing, and an engineer analysis must be made of the actual site conditions before planning times may be assessed.

FM 90-13/MCWP 3-17.1


Arm

d bn

1

st b

rigad

e S

ite 1

32

raft/

hour

Site

3

4

8 ra

ft/ho

ur

Arm

d bn

FA

bn

(86

raf

ts)

32

rafts

2

nd b

rigad

eS

ite 8

36

rafts

/hou

r

Site

9

7

2 ra

fts/h

our

Fig

ure

B-2

. R

ough

div

isio

n-cr

ossi

ng ti

me

line

H+ 1

H+ 2

H+ 3

H+ 4

H+ 5

H+ 6

H+ 7

H+8

H

Pre

p

Mec

h bn

(

55 r

afts

)P

rep

Pre

p

Eng

r bn

(50

raf

ts)

FA bn M

ech

bn

Mec

hbn

E

ngr

bnA

rmd

bn

FA b

n(3

2 ra

fts)

FM 90-13/MCWP 3-17.1


Atta

ckpo

sitio

n

Ass

ault

C

xx

x

RL

RL

Atta

ckpo

sitio

n

Atta

ckpo

sitio

n

Fig

ure

B-3

. C

OA

cro

ssin

g-ar

ea o

verla

y

Cal

l-fo

rwar

dar

ea

Cal

l-fo

rwar

dar

ea

Cal

l-fo

rwar

dar

ea

Cal

l-fo

rwar

dar

ea

Cal

l-fo

rwar

dar

ea

Cal

l-fo

rwar

dar

ea

Site

3 Site

4

Site

5 Site

7

Ass

ault

B

Hol

ding

are

a

Hol

ding

are

a

Hol

ding

are

a

Rou

te 7

Rou

te 5

Rou

te 3

Sta

ging

area

3

Sta

ging

area

5

Sta

ging

area

7

FM 90-13/MCWP 3-17.1


Table B-4. Pure company rafting requirements

Units Vehicles

Rafts Required

4 bays 5 bays 6 bays

Tank company 15 15 14 14

Mechanized company (Bradley) 15 14 7 7

Armored TF HQ 6 4 4 3

Mechanized TF HQ 6 4 4 3

Mortar platoon 8 3 2 2

Scout platoon 6 3 2 2

Engineer platoon 5 3 2 2

Division cavalry troop 24 23 16 16

ACR troop 27 25 18 17

ACR squadron HQ 6 4 3 2

155-SP artillery battery (division) 18 16 9 9

ACR tank co 15 15 14 14

FA battery (ACR) 13 13 10 7

FM 90-13/MCWP 3-17.1


H

H +

1

H +

2

H +

3

H +

4

H +

5

H +

6

H +

7

H +

8

H +

9

H +

10

Site

1

Not

use

d

Site

2

N

ot u

sed

Site

3

Pre

pM

ech

TF

-1

Eng

r B

n

Ass

ault

B

T

F-1

Site

4

Prep

Alte

rnat

e si

te

Site

5

Pre

p

A

rmd

TF

-1

A

rmd

TF

-2

F

A

Site

6

N

ot u

sed

Site

7

P

rep

M

ech

TF

-2

AD

A

Ass

ault

C

TF

-2

Fig

ure

B-4

. B

rigad

e-cr

ossi

ng ti

me

line

for

a C

OA

Eng

r bn

FM 90-13/MCWP 3-17.1


Site

Cro

ssin

gM

eans

Trip

s/H

our

Beg

inni

ng M

orni

ng N

autic

al T

wili

ght

Day

N

ight

H

H

+ 1

H +

2H

+ 3

H +

4H

+ 5

H +

6

3

8 si

x-ba

y ri

bbon

ra

fts; c

on-

vert

to

brid

ge

4026

Site

pre

p&

con

st26

raf

ts40

raf

tsC

onst

brid

ge

5B

ridge

200

200

Veh

icle

s/ho

ur

Site

pre

p/

c

onst

brid

ge20

0ve

hicl

es

7

6 si

x-ba

y ri

bbon

ra

fts; c

on-

vert

to

brid

ge

3624

Site

pre

p&

con

st24

raf

ts

4

8 ra

fts

Brid

ge

Brid

ge 2

00 v

ehic

les/

hour

Con

stbr

idge

Bri

dge

Fig

ure

B-5

. In

itial

veh

icle

-cro

ssin

g ca

pabi

lity

FM 90-13/MCWP 3-17.1


Site

Cro

ssin

gM

eans

Trip

s/H

our

Beg

inni

ng M

orni

ng N

autic

al T

wili

ght

Day

N

ight

H

H +

1H

+ 2

H +

3H

+ 4

H +

5H

+ 6

3

8 si

x-ba

y rib

bon

rafts

; con

-ve

rt to

br

idge

4026

Site

pre

p&

con

st26

raf

ts40

raf

tsC

onst

brid

ge

5B

ridge

200

200

Veh

icle

s/ho

ur

S

ite p

rep/

con

st b

ridge

200

vehi

cles

7

6 si

x-ba

y rib

bon

rafts

; con

-ve

rt to

br

idge

3624

Site

pre

p&

con

st24

raf

ts

4

8 ra

fts

Fig

ure

B-6

. F

inal

veh

icle

-cro

ssin

g ca

pabi

lity

Bri

dge

Bri

dge

200

vehi

cles

/hou

r

Con

stbr

idge

Mec

h T

F-1

Eng

rbn H

QF

ollo

w-o

n fo

rces

Arm

dT

F-1

Arm

dT

F-2

FA bnF

ield

trai

ns

85 veh

Mec

h T

F-2

Follo

w-o

n fo

rces

Brid

ge

FM 90-13/MCWP 3-17.1


Arm

d 2

Cro

ssin

g si

te 5

H-5

H-4

H-3

H-2

H-1

HH

+1H

+2H

+3H

+4H

+5H

+6

Sta

ging

are

a 3

Rou

te 3

Sup

port

ass

ault

B

Ass

ault

B

Cro

ssin

g si

te 3

Sta

ging

are

a 7

Rou

te 7

Sup

port

ass

ault

C A

ssau

lt C

Cro

ssin

g si

te 7

Sta

ging

are

a 5

Rou

te 5

R

oute

5

Sup

port

ass

ault

BC

ross

ing

site

5

Sta

ging

are

a 5

Rou

te 5

Rou

te 5

Sup

port

ass

ault

C

Mec

h T

F-1

Eng

r bn

HQ

Fol

low

-on

forc

es

Arm

d T

F-1

FA b

n

F

ollo

w-o

n fo

rces

Arm

d T

F-2

Mec

h T

F-2

Follo

w-o

n fo

rces

F

ollo

w-o

n fo

rces

F

ollo

w-o

n fo

rces

Mec

h T

F-2

F

ollo

w-o

n fo

rces

Mec

h T

F-1

F

ollo

w-o

n fo

rces

A

rmd

TF

-1A

rmd

TF

-2A

rmd

TF

-1

Fol

low

-on

forc

es

Mec

h T

F-2

F

ollo

w-o

n fo

rces

Fig

ure

B-7

. C

ross

ing-

sync

hron

izat

ion

mat

rix

Mec

h T

F-1

Eng

r

Arm

d 1

FA

Eng

r bn

HQ

Mec

h T

F-1

Mec

h T

F-2

Arm

d T

F-1

Sta

ging

ar

ea 3

Sta

ging

ar

ea 5

Sta

ging

ar

ea 7

Site

3

Site

5

Site

7

Rou

te 3

Rou

te 5

Rou

te 7

FA A

rmd

2

FM 90-13/MCWP 3-17.1


H-3

H-2

H-2

HH

+1H

+2H

+3H

+4H

+5

A/2

37

B/2

37

C/2

37

D/2

37

203

AFB

co

204

AFB

co

205

AFB

co

Mov

e to

ass

ault

site

C.

Del

iver

assa

ult

rafts

.

Del

iver

assa

ult

rafts

.

Del

iver

assa

ult

rafts

.

Pre

p R

B15

s.

Est

ablis

hE

RP

s.

Pos

ition

and

prep

are

boat

s.

Mov

e to

site

7.

Mov

e to

site

5.

Est

ablis

hE

RP

s.

Est

ablis

hE

RP

s.

Mov

e to

equi

pmen

tpa

rk 3

.

Mov

e to

equi

pmen

tpa

rk 5

.

Mov

e to

equi

pmen

tpa

rk 7

.

Pre

pare

site

3.

Pre

pare

site

7.

Pre

pare

site

5.

Bui

ldra

fts,

site

3.

Bui

ldra

fts,

site

7.

Con

stru

ct b

ridge

, site

5.

Per

form

rout

e m

aint

enan

ce o

f rou

te 3

.O

pera

te c

ross

ing

site

3.

Per

form

rout

e m

aint

enan

ce o

f rou

te 7

.

Ope

rate

cro

ssin

g si

te 7

.

Per

form

rout

e m

aint

enan

ce o

f rou

te 5

.O

pera

te c

ross

ing

site

5.

Ope

rate

rafti

ng s

ite 3

.C

onst

ruct

brid

ge, s

ite 3

.

Ope

rate

brid

ge; s

ite 5

.

Con

stru

ctbr

idge

, O

pera

te ra

fting

site

7.

Fig

ure

B-8

. E

ngin

eer

exec

utio

n m

atr

ix

Mov

e to

site

B.

Exe

cute

ass

ault-

boat

ope

ratio

ns;

assa

ult s

ite B

.

Exe

cute

ass

ault-

boat

ope

ratio

nsas

saul

t site

C.

Mov

e to

site

3.

site

7.

Ope

rate

bri

dge

site

5.

FM 90-13/MCWP 3-17.1

APPENDIX C

Crossing MeansGENERAL

Crossing means is the equipment used tocarry a force across a water obstacle. Thisequipment is specially designed to operatewithin certain limits, and commandersmust understand these limits if the force isto cross safely.

A safety matter that affects operational useis the load capacity of rafts, bridges, andequipment. The quantities shown in TableC-1, page C-4, are the normal capacities orthe design capabilities. In exceptional cir-cumstances, certain safety factors or mar-gins allow an increase in the load. Thesecapacities have been deliberately omittedhere because they are not intended for usein operational planning. The standard ordesign capabilities are provided for normalcrossings. The exceptional category isintended for special situations using theterms caution or risk crossings.

In addition to the command decisionrequired to employ caution- and risk-crossing loads, commanders must considerthe physical status of the equipment.Thus, crossing-area or crossing-force com-manders obtain a professional judgmentfrom an engineer. The commander weighsthese factors with the tactical needsbefore directing an increase in the load,keeping in mind that the equipment maybe lost for future use. River crossingshave three categories:

• Normal crossing—the vehicle's classifi-cation number is equal to or less thanthe bridge's, vehicles maintain 30-meterintervals on fixed or floating bridges,and the vehicle's speed must not exceed24 kph. Sudden stopping or accelerationis forbidden.

• Caution crossing—vehicles with a classi-fication exceeding the capacity of thebridge by 25 percent are allowed to crossunder strict traffic control. The cautionclassification number of standard fixedor floating bridges may be obtained fromFM 5-34, TC 5-210, or other appropriatetechnical manuals (TMs). The crossingrequires that vehicles remain on the cen-terline and maintain 50-meter intervals.The crossing requires that vehicles donot exceed 13 kph, stop, accelerate, andshift gears.

• Risk crossing—may be made only onstandard, prefabricated fixed and floatingbridges and in the greatest emergencies.The vehicle moves on the centerline andis the only vehicle on the bridge. Thecrossing requires that vehicles do notexceed 5 kph, stop, accelerate, and shiftgears. The vehicle's classification numbermust not exceed the published risk classi-fication for the bridge type being crossed.After the crossing and before other trafficis permitted, the engineer officer rein-spects the entire bridge for any damage.

DESCRIPTIONS OF CROSSING MEANSThis appendix supplements a generaldescription of the crossing means discussedin Chapter 3. It provides a pictorial review

as well as equipment-capability tables use-ful in selecting crossing means and plan-ning crossing operations.

Crossing Means C-1

FM 90-13/MCWP 3-17.1

Available crossing means dictate both cross-ing operations and the force-buildup rate onthe far shore. Before the commander devel-ops his tactics, he must understand how theavailable crossing means impact his abilityto mass forces on the far shore .

The following are the crossing means thatthe military use to cross a river:

• Fording vehicles.

• Amphibious vehicles.

• Aircraft.

• Boats.

• Assault launched bridges.

• Rafts.

• Bridges.

FORDING VEHICLES

Combat vehicles can ford shallow riversthat have a limited current velocity and sta-ble beds. Some vehicles have kits toincrease fording depth. Fording is possiblefor current velocities that are less than 1.5MPS. Riverbeds at fording sites must befirm and free of large rocks and otherobstructions. Vehicle-operator manuals con-tain specific depth capabilities and requiredadaptations. The AVLB and Wolverine canbe used to assist fording vehicles in deepwater.

AMPHIBIOUS VEHICLES

Some combat vehicles can swim. Bankentry and exit points must be clear ofobstructions and have slopes consistentwith the vehicle's capabilities. The cur-rent's velocity sets limits. Crews ofamphibious vehicles prepare and inspecteach vehicle before entering the water.Engineer assistance, including recoveryvehicles and standing cables, maximizesswimming opportunities.

AIRCRAFT

Army aircraft are the primary crossingmeans for dismounted infantry. Helicoptersalso lift other crossing assets from rear areasto the river and carry essential combat sup-port and critical resupply across it. See TableC-2, page C-5, for characteristics of externalloads for aircraft.

BOATS

Pneumatic assault boats are the alternatecrossing means for dismounted infantry andaccompanying elements. For light infantry,assault boats may be the only meansrequired if air resupply is available. Theycarry 12 assault troops and a two-man engi-neer crew in a silent or powered crossing.

ASSAULT LAUNCHED BRIDGES

The AVLB is an organic engineer asset thattravels with maneuvering armored andmechanized infantry formations and canquickly gap up to 15 meters for 70 MLCvehicles. The assault launcher can launchthe bridge without exposing bridge person-nel to enemy fire and can retrieve thebridge from either end (see Figure C-1 andTable C-3, page C-6).

The Wolverine will eventually replace theAVLB. The Wolverine will consist of an M1-series Abrams tank chassis modified totransport, launch, and retrieve a MLC 70bridge. The bridge will be capable of span-ning at least a 24-meter gap (see Figure C-2and Table C-4, page C-7).

RAFTS

Heavy rafts are often the initial crossingmeans for tanks and other fighting vehicles.They are faster to assemble than bridges andcan operate from multiple sites to reducetheir vulnerability. The two types of heavyrafts in the Army system are the ribbon andM4T6 (see Figures C-3 and C-4, page C-8,and Tables C-5 through C-9, pages C-9through C-12). The ribbon raft is fielded to

C-2 Crossing Means

FM 90-13/MCWP 3-17.1

engineer units while the M4T6 is maintainedin war stocks only.

BRIDGES

Rafts alone cannot handle the total volume oftraffic in the needed time. Floating bridgesare the primary means to cross the force andits supplies rapidly. The same units that pro-vide heavy rafts also provide float bridges.They often assemble bridges from the raftsused earlier.

The ribbon bridge is the primary assaultbridge because it is quick to assemble (seeFigures C-5 and C-6, page C-13, and TablesC-10 and C-11, page C-14). The M4T6, cur-rently maintained in war stocks only, wouldreplace the ribbon bridge to allow the ribbonbridge to continue to move forward with theadvancing force. Because it is man-powerintense, the M4T6 is slower to assemblethan the ribbon bridge (see Figure C-7, pageC-15, and Tables C-12 and C-13, pages C-15and C-16). Preassembly of the M4T6 floatsin rear areas significantly reduces the finalassembly time on the river.

Fixed bridges rest on the riverbanks andintermediate supports instead of floating onthe water. They span ravines as well as riv-ers. They have limited use for the initialassault because they are slow to assembleand vulnerable to enemy action. Whereappropriate, fixed bridges supplement orreplace float bridges. Engineers also usefixed bridges to repair existing damagedbridges.

The rapid construction characteristics ofthe MGB versus the Bailey bridge provideit with a better capability that can be usedwell forward in the main battle area. Sincethe Army does not currently have a tacti-cal dry-gap capability longer than 60 feet,using the MGB in this role becomes an

important operational consideration (seeFigures C-8 and C-9, page C-17, andTables C-14 through C-18, pages C-18through C-21). The primary role of theMGB is for tactical bridging in the brigadearea, while the Bailey bridge is used pri-marily as a LOC bridge. As the tactical sit-uation permits, the MGB is removed andreplaced by Bailey, timber, or steel bridges.

The Army is currently in the process ofdeveloping the HDSB to replace the MGB.The HDSB provides tactical bridging for agap-crossing capability of 40 meters with-out intermediate supports for wheeled vehi-cles up to MLC 96 and tracked vehicles upto MLC 70 (see Figures C-10 and C-11,pages C- 21 and C-22).

The M2 Bailey bridge is a truss bridge man-ually assembled by connecting panels end toend. It is used in forward areas to replaceassault bridging and the MGB. The Baileybridge system is highly labor intense butalso highly versatile. In some cases, theBailey bridge is the only tactical bridge suit-able for long spans and heavy loads becauseit can be assembled in multiple heights andwidths. The Bailey bridge is maintained inwar stocks both in the US and outside conti-nental US (OCONUS). The bridge systemcan also be assembled as a railway bridge,thus providing a relatively rapid-repaircapability (see Figure C-12, page C-22, andTable 19, page C-23).

In arctic regions and areas that experienceseasonal winter weather, a considerationthat cannot be overlooked is "ice bridging".Ice bridging is the use of bridging over athick layer of ice that covers a wet gap,such as a lake or river (see Figures C-13through C-15, pages C-24 and C-25, andTables C-20 through C-23, pages C-25through C-27).

Crossing Means C-3

FM 90-13/MCWP 3-17.1

Table C-1. Equipment-characteristic chart

Equipment Allocation Transportation CapabilitiesAssembly/Propulsion

Remarks/Limitations

Pneumatic, 15-man assault boat

L-series TOE pro-vides—• 18 per ribbon

bridge co.• 27 per corps

float bridge co.• 9 per sep bde

engr co.• 27 per corps

ribbon bridge co.

• 80 per assault-boat team.

• 21 per MGB co.• 21 per M2 co.

A 2 1/2-ton truck can carry 20 deflated boats.

An inflated boat can carry 8 men.

A deflated boat weighs 132 kg.

The boat can carry 12 sol-diers and 3 engrs with paddles or 12 soldiers and 2 engrs with an OBM or 1,531 kg of equip-ment.

Inflation time is 5 to 10 min-utes with pumps.

Paddle speed is 1.5 MPS (5 fps).

Speed with an OBM is 4.5 MPS (15 fps).

The maximum cur-rent velocity with pad-dles is 1.5 MPS (5 fps).

A 20 percent exit slope is desired.

Three pumps and 11 paddles are included with each boat.

OBMs must be requested separately.

Pneumatic, 3-man reconnais-sance boat

L-series TOE pro-vides—• 3 per combat

engr co.• 18 per corps

float bridge co.• 12 per div ribbon

bridge co. • 18 per corps rib-

bon bridge co.

The boat is car-ried by back-pack (1-man carry).

The boat and backpack weigh 26 kg.

The boat can carry 3 sol-diers with equipment or 306 kg of equipment.

Inflation time is 5 minutes with a pump.

Paddle speed is 1.0 MPS (3 fps).

The maximum cur-rent velocity is 1.5 MPS (5 fps).

One pump and 3 pad-dles are required per boat.

The boat cannot be used without an OBM.

APC M113 J-series TOE pro-vides—• 12 per engr co of

engr bn.• 1 per inf co

(mech) (BIFV).• 3 per inf co

(mech) (M113).• 9 per armored

engr co (ERI).

The APC—• Is self-

propelled.• Is a Class 13

vehicle.

The APC can carry 12 sol-diers with equipment.

Preparation time for swim-ming is 10 minutes.

The APC is track-propelled in the water.

Swimming speed is 1.6 MPS (5.3 fps).

The APC can ford up to 1.5 meters (5 feet).


Drift (meters) =

BEB-SD L-series TOE pro-vides 14 per corps ribbon bridge co.

The boat is car-ried by one 5-ton bridge truck with a cradle or one medium-lift helicopter.

The boat weighs 3,992 kg.

The boat can carry a 3-man crew and 12 soldiers with equipment or 1,996 kg of equipment.

Launch time from the cradle is 5 minutes.

The draft is—• 56 cm for normal

operations.• 66 cm when fully

loaded.• 122 cm for a

launch from the cradle.

current1.6

--------------------xriver width

meters[ ]

C-4 Crossing Means

FM 90-13/MCWP 3-17.1

BIFV J-series TOE pro-vides—

• 14 per inf co (mech) (BIFV).

• 12 per cav troop of an ACR.

• 19 per cav troop of a div cav squadron.

• 80 per assault-boat team.

The BIFV—• Is self-pro-pelled.

• Is a Class 24 vehicle.

The BIFV can carry 10 sol-ders with equipment.

Preparation time for swim-ming is 18 minutes.

The BIFV is track-propelled in the water.

Swimming speed is 2 MPS (6 fps).

The BIFV can ford up to 1.1 meters (3.5 feet).


Drift (meters) =

Drift (feet) =

Table C-1. Equipment-characteristic chart

Equipment Allocation Transportation CapabilitiesAssembly/Propulsion

Remarks/Limitations

current2

--------------------x river widthmeters[ ]

current6.6

--------------------x river widthmeters[ ]

Table C-2. Typical external loads

Table C-1. Equipment-characteristic chart (continued)

Crossing Means C-5

EquipmentWeight in Kilograms(pounds)

Remarks

M4T6 fixed spans23 feet 4 inches, Class 10030 feet 0 inches, Class 6538 feet 4 inches, Class 3545 feet 0 inches, Class 25

5,851 (12,900)7,076 (15,600)8,528 (18,800)9,480 (20,900)

Components are assembled in 8-foot 4-inch and 15-foot 0-inch incre-ments. They may be transported in packages to reduce the load.Load class may be increased by varying the deck size.

Pneumatic assault boat 131 (290) Boats are transported in a bundle or in an inflated mode.

27-foot BEB-SD 3,084 (6,800)/3,992 (8,800)

Boats are lifted in the bow-and-stem configuration.

M4T6 float-bridge componentsFloat without deckFloat with deckTwo floats with partial deck

3,039 (6,700)5,307 (11,700)7,666 (16,900

Loads are placed on the water or shore for further assembly.

Ribbon-bridge baysInterior baysEnd bays

5,443 (12,000)5,307 (11,700)

Bays are placed directly on water surfaces.

FM 90-13/MCWP 3-17.1

C-6 Crossing Means

Figure C-1. Armored vehicle-launched bridge

Table C-3. Characteristic/operation of the AVLB

Allocation Transportation Emplacement Capacity ClassLimitation/Remarks

6 per engr co, ACR

6 per engr co, separate heavybrigade

4 per engr co, heavy division

4 per engr co, corps (mech)

The AVLB—• Is carried on a

launcher (a mod-ified M48A5 or an M60A1 chas-sis).

• Weighs 15,000 kg (15 tons) (bridge only).

The spare bridge is folded on a 25-ton lowbed trailer with a 10-ton tractor (usu-ally consolidated at corps or theater level).

The AVLB—• Can be launched

in 2 to 5 minutes by a buttoned-up 2-man crew.

• Can be retrieved from either end.

• Requires that one man be exposed to guide and connect while retrieving.

The total length of the AVLB is 19.2 meters (63 feet).*

The AVLB is capa-ble of holding a Class 60 vehicle across—

• A 17.4-meter (57-foot) gap with unprepared abutments.

• An 18.3-meter (60-foot) gap with prepared abutments.

The scissors launch requires 10 meters (32 feet) of overhead clear-ance.

The maximum launch slope is—

• 28 percent uphill.• 19 percent

downhill.• 11 percent on a

side slope.

NOTE: *For crossings on the AVLB that exceed MLC 60, see the current safety message.

FM 90-13/MCWP 3-17.1

Crossing Means C-7

Table C-4. Characteristics of the Wolverine

Allocation Transportation Emplacement Capacity ClassLimitations/

Remarks

6 per engr co, ACR

6 per engr co, separate heavy bridge

4 per engr co, heavy division

4 per engr co, corps (mech)

The Wolverine—• Is carried on a launcher (a modi-fied M1-series Abrams tank chassis.)

• Weighs 12,500 kg (12.5 tons) (bridge only)

The Wolverine—• Can be launched in less than 5 minutes by a buttoned- up 2-man crew.

• Can be retrieved from either end.

• Can be recov-ered in less than 10 min-utes.

The Wolverine—• Can hold a Class 70 vehi-cle.

• Expands to a total length of 24 meters.

The launcher and bridge has a maxi-mum speed of 83 kph.

The Wolverine—• Can ford up to a depth of 122 cm (w/o a kit).

• Will replace the AVLB one for one.

Figure C-2. Wolverine

FM 90-13/MCWP 3-17.1

C-8 Crossing Means

Figure C-4. M4T6 raft

Figure C-3. Ribbon raft

FM 90-13/MCWP 3-17.1

Crossing Means C-9

Table C-5. Launch restrictions

CharacteristicsFree

Launch Controlled

LaunchHigh-Bank

Launch

Minimum depth of water required in centimeters (inches)

Ramp bay 112 (44)Interior bay 92 (36)2

76 (30)1 76 (30)2

Bank-height restrictions in meters (feet)

0-1.5 (0-5) 0 1.5 - 8.5 (5 - 28)

Bank-slope restrictions 0-30 percent 0-20 percent Level the ground unless the front of the truck is restrained.

NOTES:1 This is the recommended water depth. The launch could technically be conducted in 43 cen-timeters (17 inches) of water.2 The launch is based on a 10 percent slope with the transporter backed into the water. The required water depth for a 30 percent slope with a 1.5-meter (5-foot) bank height is 183 centime-ters (72 inches). Interpolate between these values when needed.

Table C-6. Allocation of ribbon bridge(L-series TOE)

Components Per CorpsRibbon Company

Bridge platoons 2

Interior bays 30

Ramp bays 12

BEBs 15

NOTE: The longest bridge that can be constructed is 215 meters (705 feet).

FM 90-13/MCWP 3-17.1

C-10 Crossing Means

Table C-7. Ribbon-raft design

RaftTypes

Assembly Time in Minutes

Load Space

in Meters(feet)

Classi-fication

Current Velocity in MPS (fps) and MLC

0-0.9 (0-3)

1.2(4)

1.5(5)

1.75(6)

2(7)

2.5(8)

2.7(9)

3(10)

3 bays(2 ramps/1 interior)

8 6.7(22)

LC

4545

4545

4535

4025

4015

3510

300

250

4 bays(2 ramps/2 interiors)

12 13(44)

LC

7060

7060

7060

6055*

6040*

6030*

5515*

450

5 bays(2 ramps/3 interiors)

15 20.1(66)

LC

7575

7570

7570

7070*

7060*

7050*

6025*

600

6 bays(2 ramps/4 interiors) wheeled/tracked

20 26.8(88)

L

C

96809670

96809675

96809670

96707070

96707070

96705555

70703030

7070

0

NOTES:1. When determining raft classification, L refers to the longitudinal rafting and C refers to conventional rafting.2. If the current’s velocity in the loading/unloading area is greater than 1.5 MPS (5 fps), then conventional rafting must be used.3. The roadway width of a ribbon raft is 4.1 meters (13 feet 5 inches).4. The draft of a fully loaded ribbon raft is 61 centimeters (24 inches).5. Vehicles should only be loaded on the interior bays.6. Each raft requires a minimum of two BEBs for propulsion.7. The assembly time for a raft increases by 50 percent at night.*Three BEBs are required for conventional rafting of 4, 5, or 6 bay rafts incurrent velocities greater than 1.5 MPS (5 fps). Conventional Longitudinal

FM 90-13/MCWP 3-17.1

Crossing Means C-11

Table C-8. Raft-crossing capabilities

River WidthMinutes per Round Trip

Rounds Trips per Hour

Number of Rafts per

CenterlineFeet Meters

246 75 7 8 1

328 100 8 7 1

410 125 9 6 1

492 150 10 6 2

610 188 11 5 2

738 225 12 5 2

861 263 14 4 3

964 300 16 3 3

1,148 350 18 3 4

1,312 400 20 3 5

1,476 450 22 2 5

1,640 500 24 2 5

1,968 600 26 2 6

2,296 700 29 2 6

2,824 800 32 1 6

2,952 900 35 1 6

3,280 1,000 38 1 6

3,808 1,100 41 1 6

3,936 1,200 45 1 6

NOTES: 1. This table is valid for ribbon and M4T6 rafts in current velocities up to and including 1.5 MPS (5 fps). This data is based on the use of crews under ideal con-ditions.2. Round-trip times include the times required to load and unload the raft.3. Crossing times will take 50 percent longer at night.4. If the river width falls between 2 columns, use the value found in the next higher column.

FM 90-13/MCWP 3-17.1

C-12 Crossing Means

Table C-9. M4T6-raft design and classification

Raft Types Assembly Times Crossing Types

Load Space inMeters (feet)


1.5 (5)

2(7)

2.5 (8)

3.5(11)

4-float raft:5 bridge trucks2 BEB-SD1 platoon

2 1/4 hours (when preas-sembled, 1 1/2 hours)

Normal 15.7(51.6)(wheeled/tracked)

5055

4550

4045

3035

Reinforced 11.6(38.3)(wheeled/tracked)

5055

5055

4550

3540


3 hours (when preassem-bled, 1 1/2 hours)

Normal 20.3(66.6)(wheeled/tracked)

5560

5055

4550

3540

Reinforced 15.2(50)(wheeled/tracked)

6065

6065

5560

4550


3 3/4 hours (when preas-sembled, 1 3/4 hours)

Reinforced 16.2(53.3)(wheeled/tracked)

6570

6570

6570

4550

NOTES:1. For methods on constructing an M4T6 raft, refer to TC 5-210.2. The roadway width for an M4T6 raft is 4.2 meters (13 feet 10 inches).3. The draft of a fully loaded M4T6 raft is 66 centimeters (29 inches).4. The assembly time for a raft increases by 50 percent at night.

FM 90-13/MCWP 3-17.1

Crossing Means C-13

Figure C-5. Ribbon bridge

The number of interior bays =

Gap (meters) - 14 6.7

or

Gap (feet) - 45 22

NOTES:1. Two ramp bays are required for all ribbon bridges.2. During daylight hours, a ribbon bridge can be con-structed at the rate of 200 meters (600 feet) per hour and during nighttime hours, at the rate of 133 meters (437 feet) per hour.3. Two hundred vehicles per hour, with 30-meter spac-ing at 16 kilometers per hour, can cross the bridge.

Figure C-6. Bridge design

FM 90-13/MCWP 3-17.1

Crossing Types


0-0.9(0-3)

1.2(4)

1.5(5)

1.75(6)

2(7)

2.5(8)

2.7(9)

3(10)

Normal:wheeledtracked

9675

9675

9670

9670

8280

6560

4545

3030

Caution:wheeledtracked

10585

10585

10080

10080

9680

7565

5050

3535

Risk:wheeledtracked

110100

110195

10590

10590

10090

8275

6565

4040

Table C-10. Determination of bridge classification

C-14 Crossing Means

Current Velocity inMPS (fps)

Number of Boats:Number of Bridge

Bays

0 to 2.0 (0 to 6.5) 1:6

2.0 to 2.6 (6.5 to 8.5) 1:3

2.7 (9) 1:2

Over 2.7 (over 9) Bridge must be anchored using an overhead cable sys-tem.

NOTE: Anchorage of ribbon bridges is normally accom-plished by tying BEBs to the downstream side of the bridge. The number of boats required is shown in the table.

Table C-11. Number of boats needed for anchorage of a ribbon bridge

FM 90-13/MCWP 3-17.1

1. The corps float bridge company (M4T6) includes six sets of M4T6s and six BEBs.

2. One set provides—• 43 meters (41 feet) of normal bridging

or• 29 meters (96 feet) of reinforced bridging

or• One 4-float normal raft

or • One 5-float normal raft

or• One 4-float reinforced raft and one 5-float reinforced

raftor

• One 6-float reinforced raft.

3. The M4T6 is normally transported using a 5-ton bridge truck. One bay of a disassembled bridge can be loaded on one 5-ton truck. Bays can also be preassembled and flown to the river using medium-lift helicopters.

Crossing Types


1.5(5)

2(7)

2.5(8)

3.5(11)

Normal

Normal:wheeled tracked

4555

4050

3545

2530


5859

5455

4951

3537

Risk:wheeledtracked

6667

6263

5960

4345

Reinforced

Normal:wheeledtracked

75 7075

6570

2730


80 79 73 4345

Risk:wheeledtracked

90 90 87 5960

Figure C-7. Allocation and transportation factors for the M4T6 bridge

Table C-12. Bridge classification for the M4T6

Crossing Means C-15

FM 90-13/MCWP 3-17.1

C-16 Crossing Means

Length for Normal

Assembly in Meters (feet)

Units Needed for Assembly

Number of Assembly

Sites

Time inHours

45.5 (150) 1 company 2 4

61 (200) 1 company 2 5

76 (250) 1 company 2 6

91.5 (300) 2 companies 3 4

106.5 (350) 2 companies 3 5

122 (400) 2 companies 4 5.5

152 (500) 2 companies 5 6

183 (600) 3 companies 6 4

213 (700) 3 companies 6 5 to 7

244 (800) 3 companies 6 6 to 8

305 (1,000) 3 companies 6 7 to 10

366 (1,200) 3 companies 6 8 to 12

NOTES:1. For methods on constructing an M4T6 bridge, refer to TC 5-210.2. The construction time for a reinforced bridge should be increased by 50 percent.3. The construction time for bridges should be increased by 50 percent at night.4. The draft of an M4T6 bridge is 101.6 centimeters (40 inches).

Table C-13. Determination of site and personnel requirements for the M4T6 bridge

FM 90-13/MCWP 3-17.1

Crossing Means C-17

Figure C-9. Allocation and transportation factors for the MGB

1. The corps MGB company includes—• Four bridge sets.• Two reinforcement sets.• Two erection sets.

2. Each MGB set requires seven 5-ton dump trucks and seven 4-ton bolster trailers for transportation.3. Each link reinforcement set requires one 5-ton dump truck and one 4-ton bolster trailer for transportation.4. Each erection set requires one 5-ton dump truck and one 4-ton bolster trailer for transportation.

Figure C-8. MGB

FM 90-13/MCWP 3-17.1

C-18 Crossing Means

Table C-14. Work parties for MGBs

Bridging Activity Work Party

4 and 5 bay SSB (7.9 to 9.8 meters or 26 to 32 feet)

1 NCO and 8 personnel

6 through 12 bay SSB (11.6 to 15.2 meters or 38 to 50 feet)


All DSBs Anchorage party (if required)

1 NCO and 24 personnel8 personnel

All DSBs with a link reinforce-ment party


Table C-15. SSB length and classification for the MGB

Bridge LengthNumber of Bays MLC

Feet Meters

26 7.9 4 70

32 9.8 5 70

38 11.6 6 40

44 13.4 7 30

50 15.2 8 30

56 17.1 9 24

62 18.9 10 20

68 20.7 11 16

74 22.6 12 16

FM 90-13/MCWP 3-17.1

Crossing Means C-19

Table C-16. Building times (good conditions) for the MGB

Bridge Types

Bridge Sizes

Daytime Hours

Nighttime Hours

Single story

5 bays 0.50 0.75

8 bays 0.75 1.00

12 bays 1.00 1.50

Double story without LRS

4 bays 0.75 1.25

8 bays 1.00 1.50

12 bays 1.50 2.00

18 bays 1.75 2.75

22 bays 2.00 3.00

Double story with LRS

13 bays 2.00 3.00

18 bays 2.75 4.00

22 bays 3.00 4.50

NOTES:1. A 25- by 20-meter assembly site is required.2. Only MBG company personnel are required for assem-bly/disassembly.3. The assembly time for bridges should be increased by 20 percent for untrained troops and 30 percent for inclem-ent weather.

FM 90-13/MCWP 3-17.1

C-20 Crossing Means

Table C-17. DSB length and classification for the MGB

Bridge Length 2E + Numberof Bays

MLC

Feet Meters Without LRS With LRS

37 11.3 1 70 --

43 13.1 2 70 --

49 14.9 3 70 --

55 16.8 4 70 --

61 18.6 5 70 --

67 20.4 6 70 --

73 22.3 7 70 --

79 24.0 8 70 --

85 26.9 9 70 --

91 27.7 10 70 --

97 29.6 11 70 --

103 31.4 12 70 --

109 33.2 13 50 70

115 35.1 14 50 70

121 36.9 15 40 70

127 38.8 16 40 70

133 40.5 17 30 70

139 42.5 18 30 70

145 44.2 19 24 70

151 46.0 20 24 70

157 47.9 21 20 70

163 49.7 22 16 70

FM 90-13/MCWP 3-17.1

Crossing Means C-21

Table 18. Estimated time for assembly of the MGB

Construction Type

Span in Meters(feet)

SS DS TS DD TD DT TT DT TT

Construction by Manpower Only One Crane

12 (40) 1 1/2

18 (60) 1 3/4 2

24 (80) 2 2 1/2 3

30 (100) 2 1/4 3 3 1/2 4 1/4

37 (120) 3 1/2 4 5 6 3/4

43 (140) 3 3/4 4 1/2 5 3/4 7 1/2 11 1/4 10 1/2

49 (160) 5 6 1/4 8 1/2 13 1/4 19 11 3/4 16 1/4

55 (180) 7 9 1/2 14 3/4 21 1/4 13 1/4 18 1/4

61 (200) 16 1/4 24 14 1/2 20 1/2

NOTES:1. A 20- by 30-meter assembly site is required.2. In addition to bridge company personnel, an assembly crew is required.3. For more information, see FM 5-34 or FM 5-277.

Figure C-10. HDSB

FM 90-13/MCWP 3-17.1

C-22 Crossing Means

Description

• The launcher and bridge components are on an ICBT, which is a HEMTT-based vehicle.

• The HDSB provides fast support bridging for LOC (from the brigade to the communications zone).

Capabilities

• One set can bridge a 40-meter gap.• The set can be constructed in 90 minutes by 14 soldiers.• One set can be constructed into two 20-meter bridges.• Bridge components are transportable by a CH-47.• The MLC for a 40-meter bridge is 96 wheeled/70 tracked.• The bridge can span a 40-meter gap without intermediate support.

Requirements

• The minimum depth of the gap can be no less than 2.7 meters below the height of the bank.

• Vehicles of MLC 100 wheeled/80 tracked can cross under a caution cross-ing.

• The weight load should not exceed 10,659 kg on the M1077 palletized-load-system flat rack.

• The bridge sections will have a service-life monitoring system.

Figure C-11. HDSB characteristics

Figure C-12. M2 Bailey bridge

FM 90-13/MCWP 3-17.1

Crossing Means C-23

Type of Construction

RatingSpan in Feet

30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210

SS

N 3030

2424

20 20 16 12 8

C 4237

3634

3331

3029

24 20 16 12

R 4742

4038

3635

3332

3030

24 19 14

DS

N 7570

7565

6060

5055

4045

3030

20 16 12 8

C 8376

7773

6869

6060

5050

3739

3032

23 18 14

R 8884

8579

7875

6664

5555

4244

3436

2730

21 17

TS

N 8580

6565

5055

3540

3035

20 16 12 8 4

C 9590

7475

5760

4749

3841

3133

24 18 15 10

R 100*90*

8282

6466

5254

4345

3538

2931

22 17 13

DD

N 8080

6570

4555

3545

3035

24 16 12 8

C 8690

7276

5761

4750

3942

3235

25 19 15

R 9690

8083

6468

5356

4448

3640

3033

24 18

TD

N 9090*

7580

5560

4555

3545

3035

20 16 12

C 100*90*

8390*

6572

5762

4751

3741

3134

24 18

R 100*90*

9190*

7480

6470

5458

4548

3740

2932

22

DT

N 7080

7070

6060

5555

4550

3545

3035

20 16

C 8090*

8090*

7785

6978

5764

4858

3943

3236

25

R 9090*

8890*

8590*

8089

6474

5560

4651

3843

3135

TT

N 8075

7070

5560

4555

3540

24

C 10090*

8090*

6675

5966

4852

3843

R 100*90*

9090*

7787

6877

5562

4651

Notes: N = Normal C = Caution R = Risk 1. Upper figure represents wheeled load class. 2. Lower figure represents tracked load class. * Limited by roadway width.

Table C-19. Classes of the M2 Bailey bridge

FM 90-13/MCWP 3-17.1

C-24 Crossing Means

60

50

40

30

20

10

50302010 40 60

Veh

icle

cla

ss

C x S = 1.0 0.8 0.6 0.4

0

Ice thickness in inches

Class (wheeled) =

Class (tracked) =

Legend:T = Ice thickness in inches (see Table C-20)C = Color factor (see Table C-21, page C-26)S = Strength factor (see Table C-22, page C-26)

T2

C× S×25

-------------------------

T2

C× S×20

-------------------------

Figure C-13. Determining the class of ice

Figure C-14. Required ice thickness for wheeled vehicles

FM 90-13/MCWP 3-17.1

Crossing Means C-25

60

50

40

30

20

10

50302010 40 60

Veh

icle

cla

ss

CXS = 1.0 0.8 0.6 0.4

0

Personnel

Ice-Thickness Requirements in Inches

StrongC=1, S=1

MediumC=0.8, S=0.8

WeakC=0.7, S=0.6

On skis 1.5 2 3

In a file formation with 2-meter intervals

3 4 5

On snowmobiles 3 4 5

Figure C-15. Required ice thickness for tracked vehicles

Ice thickness in inches

Table C-20. Ice-depth requirements

FM 90-13/MCWP 3-17.1

C-26 Crossing Means

Factor Characteristics

C = 1 Ice is clear (transparent)

C = 0.9 Ice is semiclear

C = 0.8 Ice is white

C = 0.7 Ice is discolored (stained brown or yellow)

Table C-21. Color factor

Factor Characteristics

S = 1 Ice is solid, and temperatures have remained at or below freezing for the previous week.

S = 0.9 Ice is solid, and temperatures have been above freezing during the day but drop below freezing dur-ing the night.

S = 0.8 Ice is solid, and water is running on the surface from runnoff or overflow.

S = 0.7 Ice is not solid, and water or air pockets are found in between layers of ice.

S = 0.6 An air pocket is under the ice, so the ice is not float-ing on the water underneath.

Table C-22. Strength factor

FM 90-13/MCWP 3-17.1

Crossing Means C-27

Table B-23. Method for determining vehicle distance

Vehicle Class (wheeled or tracked)

Required Ice Thick-ness in Centimeters

Distance Between Vehicles in Meters

(about 100 x ice thick-ness [in cm])

1 11 11

2 15 15

3 18 18

4 21 21

5 23 23

10 33 33

15 40 40

20 46 46‘

25 51 51

30 56 56

35 61 61

40 65 65

50 72 72

60 79 79

70 85 85

80 91 91

Before using the table, see remarks below:

1. If the air temperature has been above freezing for more than 6 of the past 24 hours, multiply the vehicle class by 1.3 to obtain the required ice thickness. If the air temperature stays above freezing for 2 hours or more, the ice starts to lose strength, and the table no longer represents safe conditions. A rapid and unusually large temperature drop causes the ice to become brittle, and travel may not be safe for a period of 24 hours.2. For the distance required between two vehicles of different classes, use the distance required for the higher class.3. If you plan to park for extended periods, multiply the vehicle class by 2 to obtain the required ice thickness and maintain at least the original distance requirements. Drill a hole through the ice near the vehicle, and move if the ice begins to flood.4. The ice must have water support. Be very careful close to the shore. Very often the water level will drop after freeze-up. When this happens, the ice close to the shore may no longer have water support.5. Cracks are either dry or wet. If dry, they do not penetrate ice cover and can be ignored. If wet, multiply the vehicle class by 2 to obtain the required ice thickness, and try to drive straight across the cracks (avoid going parallel to wet cracks).

Table C-23. Method for determining vehicle distance

FM 90-13/MCWP 3-17.1

GlossaryAA assembly area

AAG Army artillery group

ACE M9 armored combat earthmover

ACR armored cavalry regiment

AD air defense

ADA air-defense artillery

ADC assistant division commander

AFB assault float bridge

alt alternate

APC armored personnel carrier

armd armored

AT antitank

attn attention

AVLB armored vehicle-launched bridge

bde brigade

BEB bridge-erection boat

BIFV Bradley infantry fighting vehicle

BMAIN brigade main CP

bn battalion

BTAC brigade tactical CP

C2 command and control

CAC crossing-area commander

Glossary-1

FM 90-13/MCWP 3-17.1

CAE crossing-area engineer

CAS close air support

cav cavalry

cbt combat

CCIR commander’s critical information requirements

CFC crossing-force commander

CFE crossing-force engineer

cm centimeter(s)

co company

COA course of action

const construction

CP command post

CSC crossing-site commander

CSS combat service support

DA Department of the Army

DAG division artillery group

DD double double

div division

DMAIN division main CP

DREAR division rear CP

DS double single

DSB double-story bridge

DT double triple

DTAC division tactical CP

2-Glossary

FM 90-13/MCWP 3-17.1

DTO division transportation officer

EA engagement area

EEP engineer equipment park

engr engineer

ERI engineer restructure initiative

ERP engineer regulating point

FA field artillery

FEBA forward edge of the battle area

FM field manual

FO forward observer

fps foot (feet) per second

FRAGO fragmentary order

FSB forward support battalion

FSCL fire-support coordination line

G2 Assistant Chief of Staff, G2 (Intelligence)

G3 Assistant Chief of Staff, G3 (Operations and Plans)

G4 Assistant Chief of Staff, G4 (Logistics)

GLLD ground-laser location indicator

HDSB heavy dry-support bridge

HEMTT heavy-expanded mobility tactical truck

HIMAD high-to-medium-altitude AD

HMMWV high-mobility multiwheeled vehicle

HQ headquarters

ICBT improved common bridge transporter

Glossary-3

FM 90-13/MCWP 3-17.1

IDP initial-delay position

inf infantry

int intermediate

IPB intelligence preparation of the battlefield

kg kilogram(s)

km kilometer(s)

kph kilometer(s) per hour

LBE load-bearing equipment

LOA limit of advance

LOC lines of communication

LRS link reinforcement set

LTR light tactical raft

LZ landing zone

M meter(s)

MCWP Marine Corps Warfighting Publication

mech mechanized

METT-T mission, enemy, terrain, troops, and time available

MGB medium-girder bridge

MLC military load class

MO Missouri

MOPP mission-oriented protective posture

MP military police

mph mile(s) per hour

MPS meter(s) per second

4-Glossary

FM 90-13/MCWP 3-17.1

MRBC multirole bridge company

MSI multispectral imagery

MTOE modified table of organization and equipment

NA not applicable

NATO North Atlantic Treaty Organization

NBC nuclear, biological, chemical

NCO noncommissioned officer

obj objective

OBM outboard motor

OCOKA observation, cover and concealment, obstacles, key terrain, andavenues of approach

OCONUS outside continental US

OPFOR opposing force

OPORD operation order

OPSEC operations security

PFS pipe fascines system

PIR priority intelligence requirements

PL phase line

PLS palletized load system

prep preparation

RAG regimental artillery group

RB ribbon bridge

RB15 rubber boat 15

RL release line

Glossary-5

FM 90-13/MCWP 3-17.1

RP release point

rpm revolution(s) per minute

RTO radio telephone operator

S2 Intelligence Officer (US Army)

S3 Operations and Training Officer (US Army)

S4 Supply Officer (US Army)

SAW squad automatic weapon

SD shallow draft

sep separate

SHORAD short-range AD

SOP standing operating procedure

SP start point

SS single single

SSB single single bridge

STANAG Standardization Agreement

TAC tactical CP

TC training circular

TCP traffic-control post

TD triple double

TF task force

TM technical manual

TOE table(s) of organization and equipment

TOW tube-launched, optically tracked, wire-guided

TRADOC United States Army Training and Doctrine Command

6-Glossary

FM 90-13/MCWP 3-17.1

TS triple single

TT triple triple

TTP tactics, techniques, and procedures

US United States

veh vehicle

w/o without

WO warning order

XO executive officer

Glossary-7

FM 90-13/MCWP 3-17.1

References-1

ReferencesSOURCES USED

These are the sources quoted or paraphrased in this publication.

Army Publications

FM 5-34. Engineer Field Data. 14 September 1987.

FM 5-250. Explosives and Demolitions. 15 June 1992.

FM 5-277. M2 Bailey Bridge. 9 May 1986.

FM 34-130. Intelligence Preparation of the Battlefield. 8 July 1994.

FM 71-3. The Armored and Mechanized Infantry Brigade. 8 January 1996.

FM 71-100. Division Operations. 28 August 1996.

FM 90-4. Air Assault Operators. 16 March 1987.

FM 90-13-1. Combined Arms Breaching Operations. 28 February 1991.

FM 100-5. Operations. 14 June 1993.

FM 100-15. Corps Operations. 29 October 1996.

FM 101-5. Staff Organization and Operations. 25 May 1984.

FM 101-5-1. Operational Terms and Symbols. 21 October 1985.

TC 5-210. Military Float Bridging Equipment. 27 December 1988.

TRADOC Pamphlet 350-14. Heavy Opposing Force (OPFOR) Tactical Handbook (S&I byUSACAC). 15 September 1994.

TRADOC Pamphlet 350-16. Light Opposing Force (OPFOR) Tactics Handbook (S&I byUSACAC). 15 September 1994.

Standardization Agreements

STANAG 2395. Opposed Water Crossing Procedures (Edition 1). 27 October 1994.

DOCUMENTS NEEDED

This document must be available to the intended users of this publication.

DA FormsDA Form 2028. Recommended Changes to Publications and Blank Forms. 1 February 1974.

FM 90-13/MCWP 3-17.1

AAAGs. See Army artillery groups (AAGs).AD sites. See air-defense (AD) sites.ADA support. See air-defense artillery

(ADA) support.ADC. See assistant division commander

(ADC).AFB company. See assault float bridge (AFB)

company.air-defense (AD) sites, 2-4air-defense artillery (ADA) support, 5-4anchorage systems, 9-5

kedge anchors, 9-6overhead cable, 9-6shore guys, 9-6

antitank (AT)craters, 1-2ditches, 1-2

APC. See armored personnel carrier (APC).approach guys, 9-6armored personnel carrier (APC), C-4Army artillery groups (AAGs), 2-7assault float bridge (AFB) company, 5-3assault wave, 8-4

first, 8-4, 8-5, 8-7, 8-18, 8-19second, 8-5, 8-6, 8-13, 8-19

assembly areas, 3-10Assistant Chief of Staff, G2 (Intelligence)

(G2), 2-6, 4-3Assistant Chief of Staff, G3 (Operations and

Plans) (G3), 3-14, 4-6, 6-7Assistant Chief of Staff, G4 (Logistics) (G4),

3-1, 3-14, 4-6assistant division commander (ADC), 3-2AT craters. See antitank (AT), craters.AT ditches. See antitank (AT), ditches.attack positions, 2-4, 3-2, 3-9, 3-10, 3-12, 4-4,

5-6, 5-7, 5-8, 5-9, 5-10, 5-11, 8-1, 8-4, 8-9, 8-10, 8-11, 8-12

AVLB. See bridges, armored vehicle-launched (AVLB).

BBEB. See bridge-erection boat (BEB).BIFV. See Bradley infantry fighting vehicle

(BIFV).boat-carrying methods

high, 8-12low, 8-12

boat-launching methodsbow first, 8-12stern first, 8-13

boat-load configuration, 8-5boat team, 8-1, 8-10, 8-12, 8-13, 8-17bottom-charting sonar, 2-3Bradley infantry fighting vehicle (BIFV), C-5breakout force, 1-3, 3-1, 5-10, 5-11bridge crossing site, 7-15bridge-erection boat (BEB), 7-11, C-4, C-5,

C-15bridgehead line, 1-3, 3-2, 3-3, 3-10, 3-14, 4-1,

5-1, 5-6, 5-8, 5-9, 5-10, 5-11bridges, 1-1

armored vehicle-launched (AVLB), 1-2, 1-3, 7-14, 7-16, C-2, C-6

Bailey, 1-4, 7-16, C-3, C-22, C-23heavy dry-support (HDSB), 1-4, 9-9,

9-10, C-3, C-21M4T6, 1-4, 7-4, 7-14, C-5, C-15, C-16medium-girder (MGB), 1-1, 1-4, 7-16, 9-9,

C-3, C-17, C-18, C-19, C-20, C-21ribbon, 1-3, 7-14, 9-4, 9-5, 9-9, C-5, C-9, C-

13, C-14Wolverine, C-2, C-7

bridging operations, 7-13, 7-14, 9-3brigade main CP (BMAIN), 3-2, 3-3, 4-4, 5-5,

5-6, 5-7, 5-8, 5-9, 5-10, 6-4brigade tactical CP (BTAC), 3-2, 3-3, 5-5, 5-6,

5-8

CC2. See command and control (C2).CAC. See crossing-area commander (CAC).

Index

Index-1

FM 90-13/MCWP 3-17.1

CAE. See crossing-area engineer (CAE).call-forward areas, 3-5, 3-9, 3-10, 3-12, 4-4,

5-6, 7-12, 7-14, 9-1, 9-2, 9-3cargo team, 8-8, 8-9CAS. See close air support (CAS).centerline, 7-9, 7-10, 7-11, 7-12, 7-13, 7-14CFC. See crossing-force commander (CFC).CFE. See crossing-force engineer (CFE).Class 5 life jackets, 8-7, 8-20, 8-21clinometers, 7-6close air support (CAS), 5-5, 5-8, 5-10COA. See course of action (COA).combat service support (CSS), 5-11command and control (C2), 1-5, 3-1, 3-14, 5-3command post (CP) tasks, 3-2command post (CP), 3-1, 3-3, 3-14company flotilla, 8-5, 8-6concealment, 2-4, 3-9, 5-6, 7-3, 7-5control measures

crossing area, 3-5, 3-9, 3-10, 3-11, 3-12, 3-14, 3-15

engineer equipment park (EEP), 3-6, 3-10, 7-12

engineer regulating point (ERP), 3-5, 3-10, 7-12, 9-1, 9-2

release line (RL), 3-5, 3-12, 3-14traffic-control post (TCP), 3-9, 3-10, 3-14waiting area, 3-5, 7-3

course of action (COA), 1-4, 4-1, 4-2, 4-3, 4-4,4-6

analysis, 4-5comparison, 4-5development, 4-3, 4-4

coxswain, 8-4, 8-5, 8-7, 8-10, 8-12, 8-13, 8-14,8-15, 8-16, 8-17, 8-18, 8-19, 8-21

coxswain’s commands, 8-15crossing-area commander (CAC), 3-3, 6-4crossing-area engineer (CAE), 3-4, 4-6, 6-6,

7-9crossing-area overlays, B-4crossing capabilities

M4T6, C-11ribbon, C-11

crossing-force commander (CFC), 3-2crossing-force engineer (CFE), 3-2crossing fundamentals, 1-4crossing means, C-2

aircraft, C-2amphibious vehicles, C-2assault launched bridges, C-2boats, C-2bridges, C-2, C-3fording vehicles, C-2rafts, C-2

crossing overlay, 3-10crossing site

planning, 7-2requirements, 7-2selection, 7-1

crossing-site commander (CSC), 3-5, 6-4, 7-10, 9-1

crossing types, 1-1deliberate, 1-3, 5-1

dry-gap, 1-3wet-gap, 1-3

hasty, 1-1dry-gap, 1-2wet-gap, 1-2

retrograde, 1-4, 3-14, 6-1delay, 6-1retirement, 6-6withdrawal, 6-6

CSC. See crossing-site commander (CSC).CSS. See combat service support (CSS).current, 2-2, 7-4, 7-5, 7-6, 7-8

DDAGs. See division artillery groups (DAGs).deception plan, 1-4deliberate river-crossing phases

I, 5-1, 5-4II, 5-1, 5-6III, 5-1, 5-8IV, 5-1, 5-9

division and brigade command post (CP)functions, 5-3

division artillery groups (DAGs), 2-7division main CP (DMAIN), 3-1, 3-2, 3-15,

5-5, 5-6, 5-8, 5-10, 5-11division rear CP (DREAR), 3-1, 3-2, 3-14,

5-5, 5-6, 5-8, 5-10, 5-11division tactical CP (DTAC), 3-1, 3-2, 5-4,

5-6, 5-8, 5-10, 5-11

2-Index

FM 90-13/MCWP 3-17.1

division transportation officer (DTO), 3-14, 4-6

DMAIN. See division main CP (DMAIN).downstream drift, 7-5, 7-7DREAR. See division rear CP (DREAR).DTAC. See division tactical CP (DTAC).DTO. See division transportation officer

(DTO).

EEEP. See control measures, engineer equip-

ment park (EEP).ERP. See control measures, engineer regu-

lating point (ERP).executive officer (XO), 3-4, 3-14, 3-15, 6-4

Ffield calculations, 7-5figure-eight course, 8-15fire-support coordination line (FSCL), 5-8floating protective systems, 9-6

antimine boom, 9-7antiswimmer net, 9-7impact boom, 9-7

fording vehicles, 8-2FSCL. See fire-support coordination line

(FSCL).full-scale rehearsals, 1-3, 1-5

GG2. See Assistant Chief of Staff, G2 (Intelli-

gence) (G2).G3. See Assistant Chief of Staff, G3 (Opera-

tions and Plans) (G3).G4. See Assistant Chief of Staff, G4 (Logis-

tics) (G4).graphic fire-control measures, 8-4guide boat, 8-5, 8-13, 8-14guide stakes, 7-4

HHDSB. See bridges, heavy dry-support

(HDSB).high-to-medium-altitude air defense

(HIMAD), 5-4, 5-6high-mobility multiwheeled vehicle

(HMMWV), 8-6, 8-11

HIMAD. See high-to-medium-altitude air de-fense (HIMAD).

HMMWW. See high-mobility multiwheeledvehicle (HMMWV).

holding area, 3-9, 3-10, 5-9, 7-13, 9-1, 9-2, 9-8holding line, 3-4, 6-3, 6-5

IICBT. See improved common bridge trans-

porter (ICBT).ice

color factor, C-26strength factor, C-26thickness, C-24, C-25

ice-depth requirements, C-25IDP. See initial-delay position (IDP).improved common bridge transporter

(ICBT), 9-9, C-22initial-delay position (IDP), 6-3Intelligence Officer (US Army) (S2), 2-1, 4-3intelligence preparation of the battlefield

(IPB), 4-2, 4-3IPB. See intelligence preparation of the bat-

tlefield (IPB).

Llimit of advance (LOA), 5-8line of sight and pace, 7-7lines of communication (LOC), 6-7LOA. See limit of advance (LOA).LOC. See lines of communication (LOC).

MM9 ACE. See M9 armored combat earth-

mover (ACE).M9 armored combat earthmover (ACE), 1-2,

5-6maps, 7-6markers

raft-guide, 7-11raft-landing, 7-11, 8-8vehicle-guide, 7-11

METT-T. See mission, enemy, terrain,troops, and time available (METT-T).

MGB. See bridges, medium-girder (MGB).military police (MP), 1-3, 1-4, 1-5, 3-1mission analysis, 2-5, 4-2

Index-3

FM 90-13/MCWP 3-17.1

mission, enemy, terrain, troops, and timeavailable (METT-T), 5-2, 5-5, 5-7, 5-8, 8-3

mission-oriented protective posture (MOPP),2-7

mock-up raft, 9-2MOPP. See mission-oriented protective pos-

ture (MOPP).Morse Code, 8-8MRBC. See multirole bridge company

(MRBC).MSI. See multispectral imagery (MSI).multirole bridge company (MRBC), 9-8, 9-9multirole-bridge-company (MRBC) concept,

9-10multispectral imagery (MSI), 2-5

Oobservation, cover and concealment, obsta-

cles, key terrain, and avenues of ap-proach (OCOKA), 2-2

obstructions, 2-3man-made underwater, 2-3mud banks, 2-3natural underwater, 2-3rocks, 2-3sand, 2-3vegetation, 2-3

OCOKA. See observation, cover and conceal-ment, obstacles, key terrain, and ave-nues of approach (OCOKA).

Operations and Training Officer (US Army)(S3), 3-14, 4-4

operations security (OPSEC), 1-4, 6-7OPSEC. See operations security (OPSEC).

PPFS. See pipe fascines system (PFS).pipe fascines system (PFS), 1-2PIR. See priority intelligence requirements

(PIR).pneumatic, 15-man assault boat, C-4preparation team, 8-9priority intelligence requirements (PIR), 2-6

Rraft

maintenance, 7-13

operations, 7-12, 7-13, 9-2refueling, 7-13site, 7-9, 7-11, 7-12

rafts, 7-9M4T6, C-2, C-8, C-12ribbon, C-2, C-8, C-10

RAGs. See regimental artillery groups(RAGs).

reconnaissancefar-shore, 8-7, 8-8ground, 7-5nearshore, 8-10team, 8-7, 8-8

regimental artillery groups (RAGs), 2-7rise, 7-6river-crossing categories

caution, C-1normal, C-1risk, C-1

river-crossing organization, 1-3assault force, 1-3, 1-5, 3-1, 7-9, 8-4, 8-9bridgehead force, 1-3, 1-5, 3-1maneuver-support force, 1-3, 1-5, 3-1, 4-1

RL. See control measures, release line (RL).rubber boats, 8-2run, 7-6

SS2. See Intelligence Officer (US Army) (S2).S3. See Operations and Training Officer (US

Army) (S3).S4. See Supply Officer (US Army) (S4).safety boat, 7-11SHORAD. See short-range air-defense

(SHORAD).short-range air-defense (SHORAD), 5-4, 5-6,

5-9slopes and degrees, 7-5, 7-6smoke production, 8-16smoke, 8-4staging area, 3-9, 3-10, 3-12, 9-2Supply Officer (US Army) (S4), 3-3support force, 8-2swimming operations, 9-4

TTAC. See tactical command post (TAC).

4-Index

FM 90-13/MCWP 3-17.1

tactical command post (TAC), 3-6TCP. See traffic-control post (TCP).terrain, 1-6

analysis, 2-2characteristics, 2-1detachments, 2-5management, 1-6

traffic control, 9-1traffic-control post (TCP), 3-9, 3-14, 5-6, 6-4,

9-1transit lights, 8-8, 8-9, 8-14, 8-15

Uunderwater reconnaissance, 2-3unit-movement-control officer, 3-5

Vvehicle-recovery team, 7-14vehicle-crossing-capability chart, B-4

Wwaiting area, 3-9, 3-10warning order (WO), 4-2, 8-2water changes, 2-3

floods, 2-3swell, 2-3tidal variation, 2-3

WO. See warning order (WO).

XXO. See executive officer (XO).

Index-5

FM 90-13/MCWP 3-17.1

By Order of the Secretary of the Army and Commander of the Marine Corps:

DENNIS J. REIMERGeneral, United States Army

Chief of Staff

DISTRIBUTION:

Active Army, Army National Guard, and US Army Reserve: To be distributed in ac-cordance with the initial distribution number 110312, requirements for FM 90-13/MCWP 3-17.1.

04286Secretary of the Army

Administrative Assistant to theJOEL B. HUDSON

26 January 1998

army - fm90-13 - river crossing operations

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