The M1 Abrams is a third-generation American main battle tank named after General Creighton Abrams and designed by Chrysler Defense (now General Dynamics Land Systems). Designed as a highly mobile main-battle tank for modern armored ground warfare,[14] the M1 is well armed and heavily armored. The Abrams introduced several notable and innovative features such as a powerful 1500 hp AGT1500 multifuel turbine engine, sophisticated Chobham composite armor, a computer fire control system and separate ammunition storage in a blow-out compartment along with NBC protection for crew safety. While the initial models of the M1 were armed with a licensed-produced 105 mm Royal Ordnance L7 gun, later variants feature a licensed Rheinmetall 120 mm L/44 for increased firepower. Weighing nearly 68 short tons , it is one of the heaviest main battle tanks in service. Three main versions of the M1 Abrams have been deployed, the M1, M1A1, and M1A2, incorporating improved armament, protection, and electronics with each new model. These improvements and other upgrades to in-service tanks have allowed this long-serving vehicle to remain in front-line service