UNITED24 - Make a charitable donation in support of Ukraine!





The following paragraphs supplement the general descriptions of acceptable crossing sites in Chapter 2. Selection of crossing sites is primarily based on the-

Conflicts between tactical and technical requirements frequently occur. Commanders evaluate the factors bearing on the problem to determine the best overall solution.


Each crossing means, except air assault, requires a type of crossing site. They can be identified as fording, assault-boat, swimming, rafting, or bridging sites. Assault battalions use either a fording or an assault-boat site (or sometimes a swimming site) as an assault site.

Both the desired scheme of maneuver and available crossing means influence crossing-site selection. The division assigns a crossing area to each lead brigade. The brigade chooses which crossing sites to use within its area. When a particular site is important to the division's tactical concept, such as for the movement of breakout forces, the division either coordinates with the affected brigade to open that bridge site or moves a bridge to that site once the brigade hands over the crossing area to the division.

Brigade commanders select final crossing sites based on tactical intelligence and their desired schemes of maneuver. Each site's physical characteristics, required engineer support, and available crossing means influence the decision, but tactical requirements are the most important.

The goal when selecting assault sites is to pick those that allow the lead battalions to cross unopposed and seize far-shore objectives rapidly. If unsuccessful at finding undefended crossing sites, the lead battalions cross under enemy fire while overwatch units provide direct and indirect suppressive fires. Assault sites may or may not coincide with rafting or bridging sites.

When selecting swimming sites, the goal is to pick those that permit fighting vehicles to rapidly enter, swim across, and exit the water with minimum assistance.

The goal when selecting rafting and bridging sites is to pick those that support the greatest volume of vehicle traffic consistent with the scheme of maneuver. Rafting and bridging sites are usually on or near major roads to minimize route preparation and maintenance. When the sites are located close together, the bridging site must be upstream of the rafting site. This will avoid potential damage that may be caused by disabled rafts drifting into the bridge.

Regardless of the crossing means, each site needs engineer reconnaissance swimmers or an engineer light diving team to cross early, reduce obstacles, and develop exit points on the far bank. Riverbanks at otherwise suitable crossing sites often need work for access to the river. Most natural soil becomes unstable under heavy traffic. This condition worsens as fording, swimming, and rafting activities carry water onto it. The required engineer effort varies with soil type, crossing means, and vehicle density. An engineer vehicle that is capable of maintaining the exit bank should be one of the first vehicles across.

Natural conditions vary widely. Banks may require little preparation, or they may be so restrictive that they limit feasible sites. Desirable site characteristics include-

Initial and subsequent entry points can vary. Available locations seldom have all the desired tactical and technical characteristics. The best routes through the crossing area normally cross the river at the technically best crossing sites. The best technical sites may not be the best tactical sites because they are well known and are heavily defended by the enemy. Forces initially crossing at less desirable locations are most likely to avoid detection and gain surprise. Moving laterally along the exit bank, forces attack the flank or rear of enemy units to seize the better crossing locations. Use of these sites allows rapid buildup of combat power.


Planners need information of potential crossing sites to evaluate their compatibility with proposed crossing plans. Generally, planners need to know-

More specifically, planners need to know the-


Discussed in the following paragraphs are some of the requirements necessary for crossing sites.


A desired feature of all sites is readily accessible entry/exit routes or paths on either bank. The approaches to the banks are checked for their ability to support the requirements (width, slope, and trafficability) of the wheeled and tracked vehicles of the crossing element. Covered and concealed approaches enhance surprise and survivability; however, multiple routes, free from obstruction, will increase crossing speed and flexibility. Exit-bank conditions often take precedence over entry-bank conditions until equipment and troops can be crossed to develop and improve the site. See Table 7-1 for depth requirements.


Depending on the crossing operation that is used, the following considerations must be given to routes and approaches:

Depending on the vehicle that is used, the following considerations must be given to routes and approaches:


Numerous waiting areas are required for equipment and troops preparing and protecting sites and for troops and vehicles preparing and/or waiting to cross. These areas should be dispersed, provide cover and concealment, and be accessible to road networks near the sites.


In general, currents less than 1.5 meters per second (MPS) are desired. Narrow segments of the river decrease equipment requirements, crossing time, and exposure time. However, resulting increased current velocities may offset any advantage. As the current's velocity increases, it decreases the ribbon bridge's ability to handle heavy military load class (MLC) vehicles. More boats will be required to keep the bridge in place and allow for heavy MLC vehicles to cross.


Ford banks may be steep and rugged for dismounted troops; however, vehicles require slopes less than 33 percent and firm soil conditions. Assault or swim banks may be steep when using assault boats for dismounted troops. Amphibious vehicles may be able to enter over low, 1-meter vertical banks, but they require sloped exits. Vertical banks of about 1 meter may be accommodated by bridge or raft ramps (see Table 7-2). Vertical bank heights for bridges using the equipment listed in the table do not change for ribbon bridges. For M4T6 and Class 60 bridges, the height of the bridge deck can be adjusted to accept a difference in bank heights; however, the limiting factor may become the longitudinal slope of the bridge.


Ford bottoms must be free from obstacles, firm, and uniform. Riverbeds may be improved with rock fill or grading equipment. Guide stakes make the crossing of the river easier for boat drivers. Assault- or swim-site bottoms must be free from obstructions that interfere with boats or the tracks of amphibious vehicles. Rafting sites must be free from obstructions that could interfere with boat operations. Bridges emplaced for lengthy periods (4 hours or more) or in strong currents require suitable riverbeds for anchorage. Engineer light diving teams from the corps Army may be used to-


Sites masked from enemy observation enhance surprise and survivability by degrading the enemy's ability to see. Using existing sites reduces preparation time but requires caution in that the enemy may have emplaced obstacles and registered artillery on the site.


A ground reconnaissance refines and confirms information gathered from other sources. Training Circular (TC) 5-210 contains details for conducting and reporting site reconnaissance. From this and other detailed reports, planners may develop charts or overlays to compare alternate sites. Unit SOPs may prescribe specific comparative methods. See Figure 7-1 for an example.


Some common relationships and field-expedient calculations that are useful during a ground reconnaissance include-


Correlating the desired maximum current velocity of 1.5 MPS with a familiar comparative unit of measure may help in estimating the current's velocity. The quick-time march rate of 120 steps per minute, with a 30-inch (or 76-centimeter) step, equates to 1.5 MPS. Other approximate correlations of 1.5 MPS include-

Determining the current's velocity is critical to effective and safe crossing operations. When it is high, more boats are required to stabilize the bridge, particularly when anchorage is not used. A reasonable estimation involves measuring a distance along the riverbank and noting the time a floating object takes to travel the same distance. Dividing the distance by the time provides the current's velocity (see Figure 7-2).


The slope of terrain is significant (for example, slopes of 7 percent or more slow movement and may require vehicles to operate in a lower gear). Slope, usually expressed as a percentage, is the amount of change in elevation (rise or fall) over a ground (horizontal) distance (see Figure 7-3).

The means to determine the percent of the slope include-

Slope may also be expressed in degrees; however, this provides angular measurements. The method is not commonly used because the relationships are more complex than desired for field use. Figure 7-5 lists some relationships of the percent of the slope to the degree of the slope.


A field-expedient means of measuring the river's width is with a compass. While standing at the waterline, fix your sight on a point on the opposite side and note the magnetic azimuth. Move upstream or downstream until the azimuth reading to the fixed point on the opposite bank is 45 degrees different than the original reading. The distance from the original point to the final point of observation is equal to the river's width (see Figure 7-6).


Current causes all surface craft to drift downstream. Each vehicle has a different formula for calculating downstream drift. Amphibious vehicles and assault boats drift more than powered boats and rafts; the latter has a greater capability to negate the effect of the current's velocity by applying more power.

Amphibious vehicles and nonpowered assault boats are generally limited to current velocities of 12.5 to 2 MPS and 1 MPS respectively (see Figure 7-7).

When crossing with amphibious vehicles and pneumatic boats, compensate for the effect of the current (see examples below).

Example 1

Entry is usually made upstream of the desired exit point. The vehicle or boat is aligned, or aimed, straight across the river, creating a head-on orientation that is perpendicular to the exit bank. However, the current produces a sideslip, downstream forward movement (see Figure 7-8). This technique requires operator training in continual adjustment to reach the objective point on the exit bank. This technique results in a uniform crossing rate in the least amount of time and is usually the desired technique.

Example 2

If the operator continues to aim the vehicle at the desired exit point, the orientation of the craft at the exit point will approximate an upstream heading. The craft's path is an arc in proportion to the current's velocity (see Figure 7-9).

Example 3

To exit at a point directly across from the entry point requires an upstream heading to compensate for the current's velocity (see Figure 7-10).

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

Terrain conditions may restrict the location of entry and/or exit locations. Enemy situations may require alternate techniques. For example, when aiming at the downstream exit point, the craft moves at a greater speed relative to the banks after entry than it does as it nears the exit due to the current's velocity. Use of this technique may be favored when the enemy has a better observation of the entry bank rather than the exit bank. Watercraft moving fast and at a changing rate are more difficult to engage effectively.


The assault force seizes a far-shore objective and then clears in zone to secure the crossing sites from direct fire. Quick reinforcement with armored fighting vehicles is critical when the initial assault is dismounted.

Given the vital need to rapidly build combat power on the far shore, the lead brigades should swim the fighting vehicles of the follow-on battalions whenever practical to save the rafts for the tanks. Rafts are usually the initial means for crossing nonswimming vehicles, particularly tanks, on wide, unfordable rivers. It may be possible to bridge immediately after the assault across the river; however, rafting is normally first because rafts-

Raft assembly begins on order, not according to a preplanned schedule, even though the crossing plan has an estimated start time. Unless the division commander directs otherwise, the brigade commander, advised by his CAE, decides when to begin rafting. This is always after eliminating enemy direct fire on the site and usually after neutralizing observed indirect fire. Massed enemy indirect fire can cover an entire rafting site. The force neutralizes observed indirect fire by suppressing it and obscuring the crossing sites.


The brigade commander also decides when bank preparation can begin, or he may delegate this decision to his CAE. The decision is based on the estimated time required to secure the area. By initially spending extra time and effort preparing a bank, maintenance problems can be avoided during rafting operations.

The key to rapid and effective bank preparation is good engineer reconnaissance, which permits engineers to arrive at the site early, organized and equipped to perform specific tasks to improve the approach. The same is true on the exit bank. Poor bank conditions require early priority for raft movement of engineer equipment across the river. Time spent preparing the exit banks before passing heavy traffic greatly reduces maintenance of the crossing site and speeds force buildup later. Two entry and exit points per centerline make it possible to alternately use one while maintaining the other.


Each lead brigade should have at least two rafting sites, each of which has one to three raft centerlines. The terrain, routes, and tactical plan determine their location. However, they should not be closer together than 300 meters to avoid congestion and the risk that enemy artillery concentrations will impact on more than one site during a barrage. Engineers prepare alternate sites as soon as possible to permit the relocation of rafts in case of enemy action or bank deterioration. Each rafting site also contains the control and operation structure that is necessary to conduct rafting operations (see Figure 7-11).

Engineer platoon leaders are in charge of rafting sites. Each site has one to three active centerlines spaced 100 to 300 meters apart. With the 100-meter minimum distance between centerlines, collisions between rafts on adjacent centerlines are avoided and the effects of artillery are reduced. However, spacing centerlines farther than 300 meters apart stretches the ability of one's unit to control both land approaches and water operations. Each crossing site has at least one alternate centerline. The CSC switches to the alternate centerline when necessary due to enemy fire or bank maintenance.

The centerline has an embarkation point on the near bank, a debarkation point on the far bank, and rafts operating between these two points. The number of rafts on a centerline depends on the river's width and the unit's control (see Appendix C). Maintaining bridge-unit integrity on centerlines and crossing sites is critical. It simplifies the maintenance and operation of rafts and significantly improves control on the water, as all raft commanders and boat operators have trained together. On any centerline, rafts must be the same type and configuration.

Centerlines are marked to guide vehicles approaching and leaving the water and to guide rafts to the correct landing points. Marker stakes or panels are used during daylight, and dim lights (covered flashlights or chemical lights) are used at night (see Figure 7-12). The raft commander designates the location of the markers depending on the terrain and the current's velocity. Markers include the following:

Each rafting site contains at least one safety boat, normally a bridge-erection boat (BEB), for troop and equipment recovery. The bridge 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 not wear boots or load-bearing equipment (LBE). The safety boat also has a float with an attached line for rescuing troops in the water, a boat hook, rocket-propelled lifelines (if available), and night-vision goggles (for the boat commander, primarily). It has a radio on the bridge company net. The safety boat maintains its station 50 meters downstream of the raft site.

As soon as possible, a safety line should be run across the river 100 meters downstream from the last centerline. This line is fastened to the banks and kept afloat by life jackets attached to the line every 30 meters. This rope acts as a catch rope for troops who may fall overboard during rafting operations, especially during limited visibility. The safety line does not replace the need for a safety boat but helps in case several soldiers fall into the river.

Each crossing site requires an EEP located where the equipment will be accessible to the crossing site. Traffic between the EEP and the riverbank should use a separate route to avoid congestion with the crossing.

Each rafting site requires a place along the friendly shore, downstream of the centerlines, for immediate raft repairs. The maintenance area requires an access point to the river for the removal and launching of bays and boats. Additional equipment desired at the maintenance area includes-


Units begin their preparations for rafting operations at a staging area. There, they receive briefings, conduct inspections, and rehearse the rafting operation. Personnel will be issued life jackets and given instructions on what to do upon loading onto the raft.

When ordered to begin rafting, the site commander directs personnel at the ERP in the call-forward area to begin sending raft loads forward. Units proceed from a staging area to the call-forward area where engineers at the ERP organize them into raft loads and send them down to the river. Any points along the route that may cause confusion, such as intersections, are either manned with a guide or are marked to ensure that the vehicles do not get lost. Once a raft load nears the river, the platoon leader directs it to the appropriate centerline. The platoon leader controls the flow of traffic to the centerlines to ensure that there is a smooth flow of traffic and that centerlines are neither congested nor underused. He establishes the timing required so that raft loads leave the call-forward area and match up with a returning empty raft.

When a raft load reaches the riverbank, it is met by an engineer centerline guide. He stops the raft load 3 meters from the edge of the water and holds it there for the raft commander. The raft commander guides the vehicles of the raft load onto the raft. The raft crew chocks the vehicles and ensures that all passengers are wearing life jackets. The passengers do not dismount from their vehicles. All hatches are opened to allow quick exit of the vehicle in case of an emergency. Upon reaching the debarkation point, the raft commander guides the vehicles off the raft. After the raft load debarks, the raft commander checks with the centerline guide for any return vehicles and returns to the embarkation point.

Once on the far shore, the centerline guide directs the raft load to the far-shore holding area where it re-forms. The passengers remove their life jackets, which are collected and returned by an engineer team to the staging area for future loads.


During rafting operations, rafts require stops for refueling, preventive maintenance, and minor repairs. The efficiency of the crossing depends on all rafts having enough fuel and minimal lost time for refueling and normal maintenance. This efficiency requires the bridge company to intensely manage raft maintenance and to operate the maintenance area much like a pit crew in an automobile race. When directed, a raft pulls off the centerline and moves to the crossing-site maintenance area.

With the raft secured, the crew begins refueling and maintenance operations. Mechanics assess and repair any minor damages to the raft and the boats. Fuel handlers run fuel lines from the fuel to both bridge boats and fuel them simultaneously. If no major deficiencies are identified, the entire process requires 20 minutes. If major deficiencies are identified on the boat, it is removed from the raft and replaced with an awaiting spare. The boat will then be removed from the water and sent back to the EEP for repair. When refueling and maintenance operations are finished, the raft returns to its centerline and another raft is directed in for maintenance and refueling.

Since the maintenance and refueling operation is continuous and requires removing a raft from the operation for up to 30 minutes, it is important to account for this reduction in capabilities when planning the operation. Generally, it is unnecessary to refuel for the first two hours after rafting begins. Once raft maintenance and refueling begin, one of the six rafts in each bridge company is unavailable for carrying vehicles across a river at all times.

When a raft becomes damaged and needs immediate repair, the raft commander moves it to the maintenance area. If a raft loses a boat and cannot make it to the maintenance area without assistance, the raft commander contacts the maintenance supervisor, who sends the maintenance boat out to assist. If a raft is still carrying a load, the raft commander decides on which bank he will disembark the load. Once in the maintenance area, mechanics determine the extent of the damage. If the damage requires significant repair, the raft will be removed and replaced with a spare. Lengthy equipment repairs are done at the EEP.


Bridges replace or supplement rafts once enemy-observed indirect fire is eliminated. Each lead brigade should convert at least one rafting site to a bridge site as soon as possible, while keeping other raft sites in operation until a second bridge is in place. Bridges have greater traffic-flow rates than rafts. The ribbon bridge is the preferred initial bridge, since it is faster to assemble and easier to move than other types. Once assembled, all float bridges have a crossing rate of 200 vehicles per hour, with a vehicle speed of 15 mph. As with rafts, bridge assembly begins on order, not according to a preplanned schedule. Since vehicles cross rivers much faster on bridges than on rafts, early bridge assembly is desirable but must be weighed against the risk that the enemy can still bring indirect fires down on an immobile bridge. The brigade commander decides when to begin, with advice from his engineer. He may delegate this decision to his CAE.

Bridges need protection. AD, counterfires, and ground-security elements are necessary to defeat enemy attacks. Booms on the river protect bridges from damage caused by waterborne munitions and debris. Antidiver nets are placed upstream and downstream to protect bridges from swimmers or underwater demolition teams. Engineer light diving teams may be employed to reduce debris along the debris-collection side of the upstream boom using portable hydraulic chain saws.

Bridges are vulnerable to enemy long-range artillery fire and air attack even after the assault force clears enemy forces from the exit bank. For this reason, ribbon bridges are used for a limited period of time, normally two to four hours, before engineer bridge units break them apart and move them to other sites. When the division uses this pulse-bridging tactic, its units wait to cross in staging areas and surge across when bridges are in place.

Enemy air superiority over the river may prohibit bridge assembly. A sustained enemy air attack forces engineers to break established float bridges into rafts. This minimizes the destruction of scarce bridging assets yet enables the crossing to continue, though at a slower pace. Engineers prepare alternate sites and position spare equipment nearby in case of enemy action.

As the danger from enemy action lessens, engineers use the more slowly assembled LOC and M4T6 bridges to augment and then replace the tactical bridges (ribbon bridge or AVLB). They do this as soon as possible to move ribbon bridges forward to other crossing operations.

Enemy bridges captured by the lead brigades are a bonus and speed the crossing. Engineers with the lead brigades neutralize explosive devices and reinforce weak or damaged bridge structures whether the damage is above or below the waterline. Commanders rarely base the success of an operation solely on the seizure of intact bridges.


A bridging operation requires a continuous traffic flow to the river. Units must be quickly briefed and moved to the crossing site. To accomplish this, units receive briefings in the staging areas from traffic-control personnel. There is no intermediate call-forward area. To control crossing vehicles, the engineers from the bridge unit set up an ERP at the bridge's access points on each side of the river. These engineers guide vehicles onto and across the bridge, ensure the proper speed and spacing of vehicles on the bridge, and prevent vehicles too heavy for the bridge from trying to cross.

A recovery team is stationed on the far shore to remove any damaged vehicles from the bridge. The recovery team consists of a medium or heavy recovery vehicle and crew, with sufficient winch cable to reach across the bridge. A typical site setup is shown in Figure 7-13. The bridge site must have several possible centerlines with adequate road networks from the unit's staging areas. Individual centerlines are spaced greater than 300 meters apart to reduce the effect of enemy artillery and air attacks.

Any method can be used to mark the route to the bridge as long as markers are visible to the operators of the vehicles and are masked to observation from above. As the vehicle approaches the bridge's edge, markers are spaced 30 meters apart to assist operators in visualizing the required vehicle interval on the bridge.


At night and during limited visibility, bridge company soldiers guide the vehicles across the bridge to prevent them from driving over its side and to help them to maintain the correct crossing speed.


Soldiers must not ground-guide vehicles by walking in front of them. Instead, soldiers should be placed as guides in stationary positions at reasonable intervals along the bridge.

Guides carry flashlights or chemical lights to guide the vehicles. The first guide momentarily stops the vehicle at the ramp and guides it onto the bridge. He then shields the lights with his body and steps out of the roadway. The second guide, spaced about 30 meters farther along the bridge, unshields his lights and directs the vehicle to his location. When the vehicle operator sees a guide shield his lights, he looks further down the bridge to pick up the next lights and is guided to them. When the vehicle reaches the guide, he shields his lights and steps aside so that the next guide can pick up the direction of the vehicle. This procedure is continued across the bridge.


If the unit comes under fire while on the bridge, those vehicles that are on it continue moving to the other side and leave the area. Vehicles that are not yet on the bridge stop and go into a herringbone formation or take up concealed positions. Once all vehicles have cleared the bridge, the bridge crew will break it into rafts and disperse them to reduce their vulnerability to incoming fire.


If a vehicle breaks down on the bridge, the bridge crew will immediately attach a winch cable from the far side and drag the vehicle off the bridge. The recovery vehicle will not move onto the bridge and tow the disabled vehicle off since the critical requirement is to clear the bridge and maintain traffic flow; loss of the vehicle is far less important.


The AVLB allows the maneuver force to conduct a hasty short-gap crossing without requiring bridging assets from the corps. The AVLB allows vehicles up to 70 tons to cross over a 15-meter gap. During the launch, the AVLB presents a high profile that will reveal the breaching location. The bridge can be launched on the near shore and then recovered on the far shore and used again. Additionally, the AVLB can be overlaid on an understrength bridge allowing heavy tracked vehicles to cross. In such instances, the AVLB must be cribbed to avoid damage to the bridge. The AVLB can be placed on a stream bottom to assist vehicles fording over soft or rocky material, but caution must be used not to cause severe damage or bottom suction, rendering the bridge unrecoverable.

Overlapping several bridges and interlocking them can allow vehicles to ford rivers of greater width, but this works best when the only limiting factor is the depth of the river. In the near future, the AVLB will be replaced by the Wolverine, which can provide a 24-meter gap-crossing capability for MLC 70 vehicles. It will be transported, launched, and retrieved by an Abrams chassis with the turret removed.

The primary role of the MGB, a hand-erectable, heavy-duty bridge, is for tactical bridging in the forward main battle area. The key advantage of the MGB over other fixed bridges is its speed and ease of erection and little, if any, site preparation. During assembly, soldiers will be vulnerable to small-arms fire, indirect artillery fire, direct weapons fire, and a nuclear, biological, chemical (NBC) environment. As the situation permits and the enemy threat is reduced, the MGB would replace the AVLB to allow greater traffic across the gap. Eventually, the MGB would be removed to be relocated forward and replaced by other standard or nonstandard bridging.

As the danger from enemy action lessens, engineers use the more slowly assembled LOC bridges to augment and then replace the tactical bridges. The primary use of the panel (Bailey) bridge is a temporary LOC bridge. It can be used in forward areas to replace assault bridging and the MGB. This bridge system can also be assembled as a railway bridge, thus providing a relatively rapid repair capability. In some cases, the Bailey bridge is the only tactical bridge suitable for long spans and heavy loads because it can be assembled in multiple heights and widths. Currently, there are large operational stocks of the Bailey bridge in Europe, but there are no plans for additional procurement. Many allied nations have fielded the Compact 200 Panel Bridge that is similar to the Bailey but uses advanced alloys which give it greater strength.

Enemy bridges captured by the lead brigades are a bonus and speed the crossing. Engineers with the lead brigades neutralize explosive devices and reinforce weak or damaged bridge structures. Commanders rarely base the success of an operation solely on the seizure of intact bridges and should not incorporate it in a site-crossing plan. Targeting of such bridges for direct or indirect fire is relatively simple as both sides know the locations. In many cases, the load classification of civilian bridges is not enough for heavy vehicles such as tanks. If used in defensive or retrograde crossings, civilian bridges should supplement other crossing techniques.

Join the GlobalSecurity.org mailing list