The challenge is to minimize the river's impact on the commander's ability to maneuver. The force is vulnerable while crossing, as it must break its movement formations, concentrate at crossing points, and reform on the far shore before continuing to maneuver. The tactical commander cannot effectively fight his force while it is split by a river. He must reduce this vulnerability by decreasing his force's exposure time. The best method is to cross rivers in stride as a continuation of the tactical operation, whether in the offense or retrograde. Only as a last resort should the force pause to build up combat power or crossing means before crossing. This chapter introduces river-crossing operations by discussing the characteristics of this special, difficult, and dangerous task.
TYPES OF CROSSINGS
HASTYA hasty river crossing is a continuation of an attack across the river with no intentional pause at the water to prepare, so that there is no loss of momentum. This is possible when enemy resistance is weak and the river is not a severe obstacle.
A hasty river crossing is preferable to a deliberate crossing. A hasty river crossing features decentralized control at the brigade level. The brigade may use organic, existing, or expedient crossing means, but additional support from the division or corps is often necessary due to the bridge companies being controlled at corps level. That support is only available when those headquarters have taken purposeful action to position the assets at the right time and place to make a brigade hasty crossing feasible. Coordination for support must be made early in the planning process.
Small gaps that prohibit vehicles from self-bridging are encountered more frequently than large gaps that require extensive bridging. Each maneuver force should task-organize itself with organic mobile crossing assets that enable it to install bridges quickly, cross small gaps, and recover the bridges for future crossings. Follow-on bridges, such as the medium-girder bridge (MGB), may need to be positioned before assault bridges are removed at these minor gaps. The two types of hasty crossings are the dry- and wet-gap crossings.
HASTY DRY-GAP CROSSINGAntitank (AT) ditches and craters are normally what maneuver forces encounter as a dry-gap-crossing obstacle. Dry riverbeds may also present a crossing problem. Maneuver forces can use the M9 armored combat earthmover (ACE) to push down the sides of ditches or to fill in craters. Substantial fill material placed in the dry gaps allows the passage of combat tracked vehicles. The crossing site can be improved and maintained for wheeled-traffic use by follow-on forces.
The armored vehicle-launched bridge (AVLB) is particularly suited for spanning streambeds, AT ditches, craters, canals, partially blown bridges, and similar obstacles. It can be launched and recovered in less than 5 minutes. The AVLB, like the M9 ACE, is organic to combat engineer companies for use in hasty crossings of short gaps. The AVLB should be left in place across the gap only as long as it takes to cross the maneuver unit it is traveling with, then replaced with other fixed bridging, if necessary.
HASTY WET-GAP CROSSINGThe depth and width of the wet gap, bank conditions, and the current's velocity will determine if the maneuver force can cross by fording, swimming, or employing the AVLB or if other bridging assets are required. Identifying wet gaps early and deploying the required resources allow hasty crossings of known or anticipated gaps to occur. Two factors should be considered when swimming vehicles through wet gaps-the current's velocity and the bank conditions.
Because vehicles drain rapidly when exiting, initially firm banks tend to deteriorate rapidly from multiple uses of the same exit point. The existence of mud or surface irregularities further degrades the percent of the slope that the swimming vehicle can overcome. When selecting a fording site in a wet-gap crossing, the depth of the water is the most significant factor. The depth of the water in one crossing area may change due to bottom surface mud or irregularities (boulders or pot holes). The AVLB is ideally suited to allow hasty wet-gap crossings, requiring only that the supported maneuver force eliminate enemy direct and observed indirect fires. The crossing means will need to be replaced by other bridging assets as soon as possible to allow the AVLB to remain with its supported unit.
If possible, the force crosses the water obstacle at multiple points across a broad front. It makes the crossing as soon as its elements reach the obstacle, whether by day or night. As the bulk of the force crosses the water, minimum forces remain to secure the crossing sites.
Expedient crossing means may be used if readily available and can be transported to the crossing site. The reconnaissance party should note material or existing features that could be used as expedient crossing devices. These include culvert pipe, lumber or cut timber, or war-damaged equipment. The pipe fascines system (PFS), which consists of bundles of 8-inch, high-density, plastic pipes chained together, can fill gaps up to 9 meters deep and support up to 70 tons. The PFS is transported by an AVLB after the bridge is downloaded and emplaced into the gap.
A well-practiced standing operating procedure (SOP) reduces the necessary planning and preparation time. A concise order, clearly articulating the commander's intent, allows exploitation wherever subordinate units successfully force a crossing. When possible, advance elements seize existing crossing means intact and ahead of the main body.
When facing negligible or light enemy resistance on both banks, the force does not have to clear all enemy forces from the river to conduct a hasty crossing. It capitalizes on the speed of the crossing and the limited ability of the enemy to effectively oppose the crossing.
DELIBERATEA deliberate river crossing is conducted when-
Opposition from a strong defending enemy can require a deliberate crossing. A deliberate river crossing is an attack across the river after a halt to make the detailed preparations necessary to ensure success. It is characterized by-
- A significant water obstacle.
- Strong enemy resistance.
- The necessity to clear entry and/or exit banks of enemy forces.
A deliberate river crossing involves the following:
- Centralized division planning and control.
- Thorough preparations, to include the time to perform extensive reconnaissance and full-scale rehearsals, develop alternate traffic routes, and stockpile logistics.
- The massing of forces and crossing equipment.
The deliberate river-crossing organization is as follows:
- An assault force that seizes the far-shore objective and eliminates direct fire on the crossing site.
- A maneuver-support force that consists of corps combat engineers, bridge companies, military police (MP), and chemical units which provide crossing means, traffic control, and obscuration.
- A bridgehead force that attacks from the far-shore objective to secure the bridgehead, eliminating direct fire and observed indirect fire on the crossing area.
Once the river crossing is complete (bridgehead line is secured), a breakout force crosses the river behind the bridgehead force and attacks out of the bridgehead. This force is normally not a part of the unit that conducted the river crossing.
The two types of deliberate crossings are wet- and dry-gap crossings.
DELIBERATE WET-GAP CROSSINGThe deliberate wet-gap crossing is divided into the following three phases: assault, rafting, and bridging. These phases may occur in sequence or concurrently. The objective in deliberate wet-gap crossings is to project combat power to the exit bank at a faster rate than the enemy can concentrate forces for a counterattack. To do this, the commander may elect to first construct rafts for nonswimming vehicles while swimming the fighting vehicles across. Bridge construction is started when observed indirect fire has been eliminated. If the tactical situation allows the elimination of the rafting phase, bridging efforts should begin immediately. This may be a suitable option considering the high speed of employing systems like the ribbon bridge.
DELIBERATE DRY-GAP CROSSINGDeliberate dry-gap crossings are generally determined by the strength of the enemy's defenses or the magnitude of the gap. If possible, using the M9 ACE or the AVLB is preferred. The MGB, the Bailey bridge, the M4T6 dry-span bridge and, in the near future, the heavy dry-support bridge (HDSB) are used to span larger dry gaps. These assets are labor-intensive and expose personnel to enemy fire during construction but provide stable gap-crossing support for continuous operations.
RETROGRADEA retrograde river crossing is a movement to the rear across a water obstacle while in contact with the enemy. The forces conducting the crossing establish a defense on the exit bank or continue the retrograde to the defensive positions beyond the water obstacle. A retrograde river crossing features centralized planning and control because of the limited crossing means. It has the same amount of detailed planning as for a deliberate offensive crossing. Failure of a retrograde crossing may lead to losing a significant amount of friendly forces.
SURPRISEThe range and lethality of modern weapons allow even a small force to defeat a larger exposed force caught in an unfavorable position. A river provides this possibility by-
- Limiting a force to a small number of crossing sites.
- Splitting the force's combat power on separate banks.
- Exposing the force to fires while on the water.
Surprise minimizes these disadvantages; forces that fail to achieve surprise may also fail in the crossing attempt.
A deception plan is a key element of surprise. It reinforces the enemy's predisposition to believe that the force will take a particular course of action (COA). The enemy usually expects a crossing; however, it does not know where or when. A deception plan that employs reconnaissance, site preparations, force buildup, and preparatory fires at a time or location other than the intended crossing area may delay an effective enemy response to the true crossing.
The usual operations security (OPSEC) measures are also important. Commanders enforce camouflage, noise, thermal, electromagnetic, and light discipline. In particular, commanders closely control movement and concealment of river-crossing equipment and other obvious river-crossing preparations. Despite modern intelligence-gathering technology, the skillful use of night, smoke, fog, and bad weather for obscuration is still effective.
EXTENSIVE PREPARATIONComprehensive intelligence of the enemy's composition and disposition and crossing-area terrain must be developed early, since planning depends on an accurate and complete intelligence picture.
Supporting forces, which typically include engineer battalions, bridge companies, air-defense batteries, smoke-generation companies, and MP companies, must link up early. They immediately begin crossing preparations and are available to train the crossing force during rehearsals.
Commanders plan and initiate deceptive operations early to mask the actual preparation. These operations should conceal both the time and location of the crossing, so they begin before and continue throughout the preparation period.
Work necessary to improve routes to handle the traffic volume of the crossing operation should occur early enough not to interfere with other uses of the routes. This requires a detailed traffic plan carefully synchronized with the deception plan.
Full-scale rehearsals are essential to clarify roles and procedures, train personnel, inspect equipment, develop teamwork, and ensure the unity of effort.
FLEXIBLE PLANEven successful crossings seldom go according to plan. A flexible plan enables the crossing force to adapt rapidly to changes in the situation during execution. It allows the force to salvage the loss of a crossing site or to exploit a sudden opportunity. A flexible plan for a river crossing is the result of thorough staff planning, not chance. Such a plan features-
- Multiple approach routes from assembly areas (AAs) to crossing sites.
- Lateral routes to redirect units to alternate crossing sites.
- Alternate crossing sites and staging areas to activate if enemy action closes the primaries.
- Crossing equipment held in reserve to replace losses or open alternate sites.
TRAFFIC CONTROLA river is a significant obstacle that slows and stops units, thus impeding their ability to maneuver. Units are restricted to moving in column formations along a few routes that come together at the crossing sites. Traffic control is essential to cross units at the locations and in the sequence desired. Maximum crossing efficiency is achieved through traffic control. It also prevents the formation of targets that are susceptible to destruction by artillery or air strikes. In addition, effective traffic control contributes to the flexibility of the plan by enabling commanders to change the sequence, timing, or site of crossing units. The traffic-control organization can switch units over different routes or hold them in waiting areas as directed by the tactical commander.
ORGANIZATIONCommanders use the same C2 nodes for river crossings as they do for other operations. These nodes, however, take on additional functions in river crossings. For this reason, commanders specify which nodes and staff positions have specific river-crossing planning and control duties. This may require some temporary collocation of headquarters cells (or individual augmentation) and an increase in communications means.
The tactical commander organizes his units into assault, maneuver-support, and bridgehead forces. He organizes support forces consisting of engineer, MP, and chemical units, as well as other combat-support units, into a crossing organization. This organization reports to the tactical commander's controlling headquarters. Since this is a temporary grouping, procedures that the controlling headquarters establishes must be clear, simple, and rehearsed by all elements to ensure responsive support of the plan and the unity of command.
Terrain management is an integral part of the crossing operation. The controlling headquarters assigns space for support forces to work on and for assault forces to concentrate on before crossing. Otherwise, they interfere with each other and become lucrative targets for indirect fires and enemy air attacks.
SPEEDA river crossing is a race between the crossing force and the enemy to mass combat power on the far shore. The longer the force takes to cross, the less likely it will succeed, as the enemy will defeat, in detail, the elements split by the river. Speed is so important to crossing success that extraordinary measures are justified to maintain it. The commander must allow no interference with the flow of vehicles and units once the crossing has started.
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