Difficult terrain in the early years of warfare (World War I and World War II) was that landscape that was serrated with trenches and cratered by the fall of heavy ball-type artillery which tended to obstruct passage of motor vehicles and towed and self-propelled guns thereby obstructing the momentum of the battlefield charge. Trench warfare was the norm rather than the exception in these two conflicts and the kind of obstruction they created to mass forward movement of infantry and mechanized columns sometimes created what came to be called “trench deadlock”.
To be able to break this deadlock the combatants began looking for vehicles that could fly over the trenches without becoming “ditched”. Much of the credit for this transition must go to the Landships Committee formed in February 1915 to create an Armored Fighting Vehicle that would traverse territory broken up by shellfire and trenches and still be able to respond to enemy gunfire emanating from the trenches-the contributory factor to the “trench deadlock” phenomenon.
The reason why it was decided to use tracks for traction was that a tracked vehicle would not fall into the trench as would a wheeled vehicle whereas a tracked vehicle could claw its way over the other side of the trench. During this maneuver it could continue to retaliate to enemy gunfire from behind the protection of its organic armor. The drivers were trained to align the new tank at right angles to the surface of the trench so that the chances of crossing over are better and this could be achieved with no loss of time.
But wheels too had their uses on the battlefield. Self-propelled anti-aircraft guns were built around wheels which tended to give the weapon greater mobility and maneuverability. Truck mounted guns have acquired a pre-eminent position in modern asymmetrical warfare in both the urban guerrilla context as well as the rural landscape deployment. Heavy artillery was also mounted on “halftracks”-propelled by a combination of wheels and tracks to be able to take advantage of the best of both in terms of maneuverability that wheels provide and carrying capacity of tracks.
Post World War II even though the basic conceptual structure of the armored fighting vehicle was the foundation improvements in armor, power plant, weapons and suspension. Soon with long range deployment and the availability of heavy lift aircraft and helicopters it has become possible for armored fighting vehicles of all kinds to be transported by air to the battlefield. Nations with overseas commitments have switched to what has come to be known as the “airmobile” wheeled versions that are easier to mount the aircraft ramp.
Modern armor has been upgraded with improvement in protection (the Indian version of the T-90 tank Brahma wears an appliquéd-stitched on-reactive armor around its turret) and most have added engines with greater thrust, precision guided munitions for kill with first hit, and suspension for a better ride over bumpy terrain. Here again the indigenous Indian main battle tank Arjun has a unique suspension. It uses hydrodynamics to cushion the bumpy ride. It is also claimed that its track system is so designed that the tank rides lightly over desert sand instead of sinking and requiring to be salvaged by an engineering vehicle. The modern main battle tank is characterized by high firepower, mobility and armor protection relative to other vehicles of its era. It can cross comparatively rough terrain at high speeds.
Where there are high powered vehicles of war there are bound to be difficulties along the road like water obstacles, crevasses, landmines, etc. All militaries carry with them a specialized bridge layer vehicle and an engineering support vehicle both of which can take care of most emergencies in situ.
The modern trend is to install in new generations of armored fighting vehicles a significant amphibious capability, tactically useful inland, reducing dependence on bridges. They use their tracks, sometimes with added propeller or water jets for propulsion. As long as the banks have shallow enough slopes to enter or leave the water they can cross rivers and water obstacles. Same may need pre-preparations like installing a snorkel and raising the exhaust pipe. But the ability to cross a river either by fording it or swimming across at short notice helps maintains the precious military requirement known as momentum. Where this is not inherent in the weapons platform, the army needs bridge layers to cover the gap between the two banks.
Bridging the gap
The armored vehicle-launched bridge (AVLB) is a combat support vehicle, designed to assist militaries in rapidly deploying tanks and other armored fighting vehicles across rivers. The AVLB is usually a tracked vehicle converted from a tank chassis to carry a folding metal bridge instead of weapons. The AVLB’s job is to allow armored or infantry units to cross water, when a river too deep for vehicles to wade through is reached, and no bridge is conveniently located (or sufficiently sturdy, a substantial concern when moving 60-ton tanks).
The bridge layer unfolds and launches its cargo, providing a ready-made bridge across the obstacle in only minutes. Once the span has been put in place, the AVLB vehicle detaches from the bridge, and moves aside to allow traffic to pass. Once all of the vehicles have crossed, it crosses the bridge itself and reattaches to the bridge on the other side. It then retracts the span ready to move off again. A similar procedure can be employed to allow crossings of small chasms or similar obstructions. AVLBs can carry bridges of 60 feet (18 metres) or greater in length.
By using a tank chassis, the bridge layer is able to cover the same terrain as main battle tanks, and the provision of armor allows them to operate even in the face of enemy fire. However, this is not a universal attribute: some exceptionally sturdy 6x6 or 8x8 truck chassis have lent themselves to bridge-layer applications. The Defence Research and Development Organisation in one of its first successful attempts at indigenization produced bridge-laying equipment by using the Vijayanta tank chassis as the carrier vehicle. It is now standard equipment for all strike corps to facilitate rapid movement in the area of interest.
As part of the support echelon for what is known a sappers and miners work there are several types of armored engineering vehicles available to the military. The armored engineer vehicle is based on the platform of a main battle tank; these vehicles go by different names. There is no set template for what such a vehicle will look like, yet likely features include a large dozer blade or mine ploughs, a large calibre demolition cannon, augers, winches, excavator arms and cranes, or lifting booms.
These vehicles are designed to directly conduct obstacle breaching operations and to conduct other earth-moving and engineering work on the battlefield. Some of them are built to breach minefields using explosive line charges that are rocket-propelled across an identified minefield and exploded. The mines too are broken up by the concussion.
The armored recovery vehicle (ARV) is used to repair battle- or mine-damaged as well as broken-down armored vehicles during combat, or to tow them out of the danger zone for more extensive repairs. To this end the term ”Armored Repair and Recovery Vehicle” (ARRV) is also used.
The DRDO has created an Armored Engineering and Reconnaissance Vehicle based on Sarath’s hull (License produced variant of Russian BMP-2) and is designed to carry out terrestrial and riverbed survey to facilitate construction of assault bridges across water obstacles in both offensive and defensive operations in plains, desert and reverine terrain. It has no gun and is fitted with specialized equipment, including an echo-sounder, a water current meter, a laser range finder and GPS. On the left rear of the hull, a marking system with 40 rods is fitted to mark out areas contaminated by nuclear, biological and chemical fallout. The AERVs have achieved limited series production and have entered service with the Corps of Engineers.