The development of this heavy breakthrough tank began in September 1943. It was planned to utilize certain components of the M6 tank as well as the electromechanical transmission and 100-mm gun, mounted in a turret of limited traverse with 203-mm armour protection. The vehicle was intended to assault the fortifications of the German Siegfried Line (called the Westwall by the Germans). The U.S. land forces rejected the project during the design phase. Designer Jarlang
