In the early 1960s, the US Army issued a requirement for a replacement to the ageing M41 Walker Bulldog light tank. General Motors’ Cadillac Gage division was awarded a contract for prototypes of what was officially an ‘Armoured Reconnaissance/Airborne Assault Vehicle’. The new tank, the M551 Sheridan, was superficially impressive, but the design was too ambitious for the technology of the period.
The tank’s futuristic main armament, a 152mm gun/launcher system, was an endless source of trouble. Although the concept was brilliant, the realities of trying to ‘shoehorn’ such a heavy weapon into a light tank caused problems. When firing over the forward arc, for instance, the recoil would lift the front road wheels off the ground and crew members had to brace themselves to avoid being thrown around the turret. The original idea was that the weapon could fire both conventional shells and the new Shillelagh anti-tank missile, but both suffered teething problems. As such, although the first Sheridans were completed in 1966, the new missiles were not finished in time to see use in Vietnam, and the tank used only conventional shells.
A total of more than 200 Sheridans saw service in Vietnam between 1969 and 1972, largely with armoured cavalry units. The lack of any significant threat from enemy armoured fighting vehicles (AVFs) led to the decision not to deploy the still troublesome Shillelagh missiles, but the heat and humidity accentuated the unreliability of the tank’s already temperamental electrical systems.
