Main battle tank

The US M60 Combat Tank was America's first MBT which was fielded in 1960. The fielding of the MBT effectively removed all heavy & light tanks from the inventory. Stated another way: Anything other than MBT's were not tanks.

Example: The M551 Sheridan light tank was fielded for the first time in the Vietnam War in January 1969. Since light tanks no longer existed on paper, and only MBTs existed; the M551 Sheridan was officially classified as a, "Armored Airborne Reconnaissance Assault Vehicle."