Based on the T-34, the SU-122 served as an assault gun. With the removal of the turret, an armoured superstructure was placed. Fitted in the superstructure was a modified 122mm M-30S Model 1931/1937 field howitzer. It entered production at UZTM in Sverdlovsk in December 1942, and 27 examples were built in late 1942. Another 454 were built during 1943, and when production ceased in early 1944 some 1.148 SU-122's had been built. The first SU-122's saw combat on the Volchov Front in the winter of 1942/43, and it took part in the Battle at Kursk. It proved to be effective as an assault gun, delivering direct fire during attacks on strongpoints. The guns armour penetration was less than expected and therefore a shaped charge HEAT projectile was developed, but was only accurate at short ranges and its penetration was still disapointing. In 1943, prototype named SU-122P was built, armed with a long barrelled 122mm Model 1931/37 gun, but this weapon were too large and it was not accepted for production. In place of the common awkward-looking armoured mantlet used on most SU-122s, late production models had a ball mantlet similar to that adopted on the SU-85. The germans were happy to deploy as many captured SU-122s as possible. The russians managed to capture some german PzKpfw III and StuG III tanks. Many of them did not, however, enter service within the Red Army, partly due to the lack of spare parts and ammunition to the german guns. Therefor it was decided to re-arm captured vehicles with either a 76.2mm ZiS-3 gun (SU-76i) or with a 122mm howitzer. The 122mm tanks was to be known as the SG-122A.