The Armored Gun System (AGS) was a U.S. Army competition in the 1990s to design a light tank to replace the M551 Sheridan and TOW-equipped HMMWVs. It was the ultimate incarnation of several research programs run in the 1970s with the aim of providing air-mobile light infantry forces with the firepower needed to last in the battlefield.

The M551 "Sheridan" AR/AAV was a light tank developed by the United States and named after General Philip Sheridan, of American Civil War fame. It was designed to be landed by parachute and to swim across rivers. It was armed with the technically advanced but troublesome M81/M81 Modified/M81E1 152 mm gun/launcher, which fired both conventional ammunition and the MGM-51 Shillelagh guided anti-tank missile.