ISU-152 is a Soviet heavy self-propelled artillery mount (SAU) during World War II. In the name of the machine, the abbreviation ISU means “self-propelled installation based on the IS tank” or “IS installation”; the letter “I” in addition to the standard Soviet designation “SU” for military equipment of this class was required to distinguish it from self-propelled guns of the same caliber SU-152 on another tank base. Index 152 means the caliber of the main armament of the vehicle.