The M551 Sheridan was an Armored Reconnaissance Airborne Assault
vehicle, developed by the United States, and named after Civil War
General Philip Sheridan. It was designed to have both an air drop
and swimming capability. Production began in 1966, entering the US
Army inventory in 1967. Under the urging of GEN Creighton Abrams,
the US Commander of Military Forces in Vietnam at the time, the
M-551 was rushed into combat service in Vietnam in Janurary 1969.
[3]
Because one of the primary roles of armored cavalry is
reconnaissance, the M-551's began replacing the armored cavalry's
M-48 Patton tanks in South Vietnam. By 1970, the only M-48 Pattons
remaining with an armored cavalry unit in Vietnam was with the 11th
(Blackhorse) ACR (Armored Cavalry Regiment); being a full regiment,
the 11th ACR was authorized a Tank Troop (company). Armored Cavalry
Squadrons in Vietnam, such as the 1/1 (lst Squadron, 1st Cavalry),
3/4, 3/5, 4/12, etc. all were equipped with M-551's by 1970.
[2]
During the 1960s, at the time of the M-551's entry into service,
the United States Army no longer used the heavy, medium, and light
tank classifications. The US Army had adopted the new doctrine of
Main Battle Tank (MBT). The US Army still retained the M-41 Walker
Bulldog light tank in its component, the Army National Guard, but
other than the units under going the transitional process, the
regular army only consisted of MBT's. Partly because of this
policy, the new M-551, could not be classified as a light tank. As
time elapsed, the term "light tank" became acceptable to both the
military and civilians. The M-551 Sheridan, has the distinction of
being the only US tank that was designed and built during the
1960s, and deployed directly into the Vietnam War.
It was armed with the unique MGM-51 Shillelagh gun-launched missile
system. Now retired from service, it saw combat in Vietnam,
Operation Just Cause in Panama, and during Operation Desert Shield
in Southwest Asia.
