ISU-122 - Combat History

Combat History

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 differed 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. With the same hull as the IS-2 the ISU-122 had good armour performance but more importantly very good performance with high-explosive rounds. The 121.92-mm gun had great potential, although the gun's abilities were somewhat reduced by the available projectiles and its lack of accuracy. In 1944 the BR-471 was the sole armour-piercing round available (the Germans had armour piercing rounds also, including ballistic nose and sub-caliber variants). An improved version, the BR-471B (БР-471Б) was developed in early 1945, but was available in quantity only after World War II ended. In extremis the ISU-122 engaged enemy heavy armour with OF-471 (ОФ-471) high explosive projectiles. These shells had a mass of 25 kg, a muzzle velocity of 800 m/s, and were equipped with a 3 kg TNT charge. Mechanical shock and explosion was often enough to knock out enemy AFVs without any armour penetration.

For urban combat ISU-122's were utilized as assault guns, but with a lower efficiency in comparison to the SU/ISU-152. In general Red Army commanders viewed the ISU-122 as a good assault gun. The OF-471 projectile was powerful enough against unprotected and entrenched infantry, pillboxes, and fortified buildings. In urban combat the long barrel of the 121.92-mm cannon sometimes made maneuvering difficult.

Use of the ISU-122 as a self-propelled howitzer was rare, although its maximum range of fire exceeded 14 km. Usually the ISU-122 delivered indirect fire to the enemy during rapid advances when support from towed artillery was not available.