The ISU-122 assault gun was a Soviet assault gun built on the hull of an IS-II tank instead of the older KV-I. Over 3,200 vehicles were produced in total between 1943 and 1947 before the war’s end. The ISU-122 was identical to the ISU-152 with the exception of the main gun; the ISU-122 used the more powerful 122mm D-25S that was the more effective anti-tank gun.
The ISU-122 was used as a powerful assault gun, a self-propelled howitzer, and a long-range tank destroyer, the same as with the SU-152 and ISU-152 heavy self-propelled guns in general. However these vehicles had different trends in their combat use. The primary application of the ISU-122 was as a tank destroyer, while the SU/ISU-152 tended more towards the assault gun role.