The SU-122 (from Samokhodnaya Ustanovka 122 mm) was a Soviet self-propelled howitzer or assault gun used during World War II.

[2][3] The Soviet High Command became interested in assault guns following the success of German Sturmgeschütz IIIs.

However, assault guns generally aim by orienting the entire vehicle, and were thus less suited for close combat than tanks with turrets.

[citation needed] A prototype assault gun, armed with the 122 mm howitzer and built on the German Sturmgeschütz III chassis was developed, designated SG-122.

This vehicle, the U-34, was created in the summer of 1942 at UZTM (Uralmashzavod – Uralsky Machine Building factory) design bureau, by N. W. Kurin and G. F. Ksjunin.

It used the same chassis, superstructure, engine and transmission as the U-34 and was armed with (the then new) 122 mm M-30S howitzer from F. F. Petrov's design bureau.

Trials ran from 30 November to 19 December 1942, and uncovered various faults in the design, including insufficient elevation, a flawed shell transfer mechanism, poor ventilation for the crew compartment, and the fact that the commander had to assist in operating the gun, which made him unable to successfully carry out his other duties.

They incorporated several modifications, including slightly less sloped front armor to ease production, modified layout of the fighting compartment (the location of crew member stations and ammunition racks were changed), fewer vision slots, and a periscope for the commander.

[citation needed] In January 1943, the 1433rd and 1434th self-propelled artillery regiments were sent to the Volkhov Front near Leningrad as part of the 54th Army.

This organization remained in place until the start of 1944 when the SU-122 began to be replaced by the SU-152, ISU-122 and ISU-152 heavy self-propelled guns,[11] and the SU-85 tank destroyers.

The M-30S armament proved poorly suited for purpose, in spite of its prior recommendation by the GAU RKKA artillery committee.

The howitzer took a lot of space and required both commander and gunner to operate it in order to fire.

This was unsuccessful, due to the unreliability of the howitzer's recoil mechanism and its poor anti-tank abilities.