Assault and Tactical Bridging for Armor Units

Assault and Tactical Bridging - for Armor Units by Brigadier General Philip L. Bolt4 (Ret.) The role of assault and tactical bridging has been an important one throughout U.S. military history. That role is no less important today than it has been in the past. Because main battle tanks are not amphibious, bridging can have significant tactical impact on armor operations. Is assault and tactical bridging, though, getting the attcn-tion it deserves? Waterways, both natural and manmade, are a major terrain feature in Europe and vary in size from minor streams and canals to rivers, such as the Rhinc, Meuse, Moselle, and Danube. The planner who ignores European waterways imperils the success of his operation. U.S. Army European operations during WWll are replete with examples uC the criticality ofwaterway-crossing operations. In its Moselle River crossing operation at Arnaville, 11-14 September 1944, the 5th Inlantry Division and its supporting engineers had to bridge three waterways: the Moselle Canal, not only deep but also 80 feet wide; the Rupt de Mad, a small Moselle tributary; and the Moselle River itself, approximately 2.50 feet wide. Before the operation was over, engineers had erected two Bailey bridges, two treadway bridges, one double treadway bridge, and a heavy pontoon bridge over the three obstacles. In attacking the Siegfried Line near Aachen in late September 1944, the 30th Infantry Division counted on getting tanks into the bridgehead early by using culverts designed for bridging the stream. In the area of the 117th Infantry, the banks of the stream became such a quagmire that the tank do;.er charged with preparing the banks became niired in the mud. Tanks sent to assist also became bogged down, so that it became necessary Interior and ramp sections of Ribbon Bridge can be joined to provide rafts for heavy combat vehicles. to give up and wait fur construction of a treadway bridge. In the 119th Inrantry Regiment sector, the culverts fcll apart while thc tanks dragged them to the crossing site. Even when the engineers constructed a treadway bridge. deep mud halted attempts to get tanks to the infantry. During his 1960-6 I assignment to the US. Military Liaison Mission in Potsdam, then-Lieutenant Colonel Clarke T. Baldwin observed Warsaw Pact maneuvers in East Gcr-many in which tanks crossed rivers using snorkels. I n his next assignment at Fort b o x , he stirrcd up the armor community’s interest in developing such a capability for American tanks. Study revealed that a stream un-crossable with normal tank fording capability occurs in Europe approximately every 10 kilometers. The end result was development and procurement of a deep water I f 8 ARMOR - November-December 7988 fording kit for the MW-series tanks, allowing the tanks to ford to a depth of 13-1/2 feet. Although the Marine Corps has required development of a lording kit to allow landing of its MLA1 tanks during amphibious operations, the Army has shown no interest in this capability. In fact, the Army seems to have lost interest several years ago in the deep fording capability of its forces in Europe. One can argue the practicalities ol deep water fording in Europe. The many bridges available, the difficulty in determining the depth at which a tank will find firm footing, and the requirement t o prepare ingress and egress sites are among the reasons advanced for considering the capability not worth the effort. Nevertheless, the frequent occurrence of unlordable waterways in Europe remains a fact of life, and the importance ol assault and tactical bridging has become even more important. There are other reasons for the importance to armor of assault and tactical bridging. Warsaw Pact forces have an impressive ability to "The frequent occurrence of unfordable waterways in Europe remains a fact of life, and the importance of assault and tactical bridging has become even more important" create obstacles. Antitank ditches in critical areas, particularly where movement is canalized by terrain fcatures, can slow the movement of an armored lorce to a disastrous degree. Readily available bridging offers one means to allow armored forces to rapidly cross such ditches. AirLand Battle doctrine emphasizes seizing and holding the initiative, and stresses maneuver and deep attack. The doctrine becomes meaningless without the battlefield mobility to implement it. With the Abrams tank and the Bradley fighting vehicle, the U.S. Army has the armored vehicles lo capitalize on the tactical advantages of rapid battlefield movement, and to implement thc doctrinc of AirLand Battle. However, obstacles to such movement, in the form of waterways and manmade ditches, can severely restrict the movement of armored vehicles, particularly tanks, so that the inherent advantages of such vehicles are lost. Readily available, rapidly deployable bridging is a necessity. Even where bridges exist, their number is always limited, and they are subject to battle destruction. Assault and tactical bridging can provide the means to replace suddenly destroyed bridges, or provide a greater degree of flexibility in the selection ol crossing sites. Current U.S. assault and tactical bridging capabilities applicable to armored forces include the Armored Vehicle Launched Bridge (AVLB), the Rihhon Bridge, and the Medium Girder Bridge (MGB). The first is assault bridging, and the other two are tactical bridging. The AVLB, mounted on an MCfl tank chassis, provides heavy forces with a bridge that can be emplaced The Medium Girder Bridge can be deployed to span a wide body of water. ARMOR - November-December 7988 9 rapidly under combrrt conditions. The %meter bridge can pass MLC (Maximum Load Capacity) 60 track loads across a 17-meter gap, and MLC 70 track loads across a 13- meter gap. It is found in armored cavalry regiments, heavy division engineer battalions, and separate bridge engineer companies. The Ribbon Bridge, actually based on reverse-engineering of a Soviet design, was developed by the U.S. Army Mobility Research and Development Command in conjunction with Pacific Car and Foundry Company. ConDiesel Mobile Equipment Company produces the bridge. It provides tactical elements with a rapidly deployable MLC 60 wet gap crossing capability. It consists of a modular, continuous flotation bridge system made up of interior bays and ramp bays that are transported, launched, and retrieved by a wheeled transporter/ launcher vehicle. The bridgebays are transported in a Folded position. To launch the bays, the transportcr backs partially into the water, the operator releases the bays, which automatically open lo form a 6.9- mcler section of bridge. Bridge crec-lion boats join the sections. A complete bridge set of 10 interior hays, two ramp hays, and 12 transporters can be erected at a rate of about seven meters per minute to provide an MLC 60 bridge across a 77- meter water gap. Five bays can also form a Class 60 raft. The Ribbon Bridge is found in corps engineer float bridge companies. The

MGB,

designed by the Military Vehicles and Engineering Establishment at Christchurch (now the Royal Armored Research and Development Estahlishmenl), and manufactured in England by Fairey Engineering, is a hand-erectable, prefabricated deck bridge that can he assembled into bridges of varying Current Armored Vehicle Launched Bridge, mounted on M60 chassis, is too slow to keep up with M1 units and presents weight restrictions. length. Because it can be ercctcd quickly without heavy equipment, it can be used far forward under tactical conditions. With one bridge set containing 31 meters of bridging, the MGB provides the commander with a dry-gap capability in excess of the 18-meter capability of the AVLB. With the use of two sets and a reinforcing kit, a 47-meter span can be constructed. Nominally an MLC 60 bridge, the MGB can cross Class 70 loads with a reduced bridge life (7.00() instead of 10,ooO crossings). The MGB is in corps en-gincer units. These current systems provide armored units with considerable assault and tactical bridging support. However, required improvements are underway. In the case of the Ribbon Bridge, required improvements pertain largely to obtaining a basic MLC 70 capability and a longer ramp bay to accommodate the 2-meter vertical abutment of the type found on many canals. The BMY Division of Harsco is under contract to develop the necessary improvements under the Improved Ribbon Bridge program. The AVLB as mounted on an M60 chassis is incapable of matching the mobility of the Abrams tank. The bridge is only 19 meters long, and it is an MLC 60. The Army had to establish a formal requirement for a replacement. The Heavy Assault Bridge (HAB) is now being devcloped under U.S. Army contract with the BMY Division of Harsco. Israel Military Industries (IMI), as a major subcontractor, is responsible for development of the bridge itself, while

BMY

is the launch mechanism developer and systems integrator. The HAB, with an MLC 7U load classification, will bridge wet or dry gaps of 30 meters. 10 ARMOR - November-December 7988 t The Improved Ribbon Bridge, seen in an artist's rendering, above, as it prepares to deploy from its transporter-launcher. Above, the Towed Assault Bridge, which rides on a single axle, is shown being towed to a crossing site by a tank, but other vehicles can be used. Below, the bridge in use spanning an antitank ditch. I Various modifications have been proposed or are under considera-lion for the MGB. In addition, possible long-tcrni rcplacements are in research and development, including an Israeli bridge known as the Rapid Deployment Bridge. Concerned with shipping space - both air and sea - the U.S. Marine Corps has been pursuing a different course in heavy assault bridging. Experienced in the challenge of crossing antitank ditches, the Israeli Dcfense Forces initiated development, with IMI as the contractor, of a 12-meter Towed Assault Bridge (TAB). The USMC has tested the bridge but has established no procurement plans yet. The TAB is mounted on a single axle, and a tank or other vehicle tows it to the crossing site. At the site, the vehicle is reversed - or the bridge can be switched to the front - and the bridge is pushed across the gap. Folding "horns" guide the bridge onto the far bank. The crew disconnects the bridge from the towing tank without exposure. The TAB is a rapid means 0 1 providing an MLC 70 bridge across gaps up to 10 meters. The bridge easily separates into two sections to allow transport by C-130 aircraft. It is desiped to continue functioning at the MLC 70 level after losing up to 50 per cent of its structural beams to mines, artillery, or direct fire. Deployment takes less than one minute. The Marine Corps has also contracted through the Army with 1MI (this time with BMY as a subcontractor) for prototypes of the 24- mdcr Trailer Launched Bridge (TLB-24). This bridge is towed into position and launched using hydraulic power furnished by two diesel engines mounted on the trailer. The bridge itself, with three folding sections, is in many ways I ARMOR - November-December 1988

The Heavy Assault Bridge will provide armored units with a 70-ton crossing capability over gaps up to 30 meters wide. similar to, although shorter than, the HAB bridge. It provides an MLC 70 crossing Capability of gaps up to 22 meters. Deployment is accomplished in live minutes and recovery from either end in ten. The HAB and the TLB-24 are both being designed so that they can transport and launch both types of bridge, as well as the AVLB bridge. 11 appears as if development programs are proceeding to satisfy the requirenients of both the Army and the Marine Corps. However, in thc current and prqjected budget climate, procurement of these important combat support assets may lag. Even though the two services are moving into MLC 70 bridge requirements, the services may conclude to accept the less-than-op-timnl MLC 70 capabilities of the AVLB, the Ribbon Bridge, and the MGB for now. A "Safety of Use" message on the AVLB has already placed "caution" crossing limitations, such as that the M1 tank cannot cross al speeds greater than 8 mph. The Army will certainly face an affordability problcm with the HAB because the mobility of the bridge depends on procurement of a tank chassis. Given the success to date ol Marine Corps consideration of the TAB and the TLB-24. the Army might well give some thought to procurement of these less expensive alternatives to the HAB, at least to fulfill some of its requirement. Procurement savings would be more than matched by reduction in operational and personnel costs, because neither requires a dedicated vehicle or crew. Nevertheless, the Army may consider the TLB as unsatisfactory for such reasons as its asymetri-cal roadway (half the M t track overhangs the narrow roadway) or doubts that a towed bridge could keep up with the supported unit. The Marine Corps will almost surely have to procure at least some TABS and/or TLB-24s. Its bridging capabilities are sadly lacking, and the fewAVLBs are a somewhat slender reed on which to lean. Furthermore, the AVLB does nothing to solve the shipping space problem nor the challenge of air transportability. It is notahle that newer designs and materials have greatly reduced the weight per foot of all of these new bridges. One thing is certain: The ability to cross both wet and dry gaps is an important factor in the battlelicld mobility of heavy forces. Effective assault and tactical bridging is a sure force multiplier. Bridging and battlcficld mobility are too interrc-lated for the armor community to look on gap-crossing as solely an engineer problem. The successful application of AirLand Battle doctrine may well depend on an Army-wide, cost-effective approach to providing combat elements with the bridging they need. Brigadier General Philip L. Bolte is a 1950 graduate of USMA. He served 30 years in the Army in a variety of armor and R&D assignments, including command from platoon to brigade, and combat tours in Korea and Vietnam. His R&D assignments included service as an assistant project manager of the Abrams tank and program manager of the Bradley fighting vehicle systems. He is currently a consultant and military writer. 12 ARMOR - November-December 1988