Comparing: T28 Concept vs. ISU-122S

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 T5 gun, mounted in a turret of limited traverse with 203-mm armor protection. The vehicle was intended to assault the fortifications of the German "Siegfried Line" (known as the "Westwall" to the Germans). The U.S. land forces rejected the project during the design phase. The vehicle was later modified into the T95 heavy breakthrough tank.

A heavy assault gun, built on the basis of the IS tank, was effective against German heavy tanks as well as fortifications. The prototype was built at the Chelyabinsk Kirov Plant in April 1944. The vehicle entered service in August of that year, and a total of 675 vehicles were manufactured in 1944 and 1945.