Heavy self-propelled gun. These heavy self-propelled guns, along with the ISU-152, were based on the JS-1, but instead mounted a 122mm A-19 cannon, model 1937.
The first 122mm self-propelled guns entered combat in February 1944. With a sighting range of 4000 meters, it could penetrate armor plate 150mm thick. Thus it possessed intense destructive power. In the summer of 1944, self-propelled guns would participate in Operation Bagration, where the ISU-122 proved its battle-readiness, and successfully struck and decimated their many targets, among them enemy Tigers.
In total, just over 1700 units were produced.