In May 1966, the U.S. Army developed the M551 Sheridan light tank which combined the capabilities of the M41 Walker Bulldog and M56 Scorpion. It could be rapidly deployed to conflict zones via airdrop to provide fire support or anti-armor capability. The highly-mobile, amphibious M551 featured lightweight aluminum alloy construction and was powered by a 300hp diesel engine. Main armament was a M81 152mm gun-launcher. 6 armored cavalry battalions and the 11th Armored Cavalry Regiment used M551s during the Vietnam War. They later saw action during the Invasion of Panama in 1989 and the Persian Gulf War in August 1990.