At the beginning of the World War II, Soviet tank construction returned to multi-barreled tanks. The most famous combat vehicle built under this concept was the KV-7 assault SPG. In early 1945, Experimental Plant #100 (Leningrad branch) began work on the development of a double-barrel SPG based on the ISU. The project, tentatively named the ISU-122-2, was supposed to be a typical "self-propelled gun carriage" with twin 122 mm D-25S guns. The vehicle was never built, but the designers' ideas had a direct influence on further Leningrad SPG projects.