Following the success of the German Sturmgeschutz, the Russians began to develop their own self-propelled guns to fulfil both infantry support and anti tank roles. In April 1942 development began on the first of these vehicles. Based on the T-34 chassis, the SU-122 was introduced in January 1943. It was fitted with the 122mm M-30 howitzer mounted in an armoured casemate and equiped with a TMFD gunsight (ingame). To simplify production the engine and transmission of the T-34 were retained. This also eased familiarization for crews already experienced with the T-34 The large crew compartment accommodated a crew of 5, one more than the T-34. However the main gun performed poorly in the anti armour role. This was due to the weight of its shell, which reduced the muzzle velocity. The vehicles chassis was also unreliable and suffered from frequent breakdowns. In March 1943 a second variant was introduced, the SU-122M. It was fitted with an improved main gun, the U-11 howitzer and the crew was reduced to four men. Production of the vehicle ended in November 1943 when it was replaced by the SU-152. However, until the end of the war the SU-122 saw still action on the front, like the invasion of Berlin (see left picture). However all the SU vehicles were be replaced by the ISU's, built on the KV-1 chassis, the ISU-122 was a complete new design. It mount no howitzer anymore, but an anti-tank gun. Meanwhile the other SU's that are be replace by the stronger ISU's, share there own gun.
The Design Office of Uralmashzavod wanted in march 1943 an improvend version of the SU-122. With this, an SU-85 chassis with fuselage have be used. The gun, should be replace by an 122mm D-6 howitzer wich was lighter and smaller then the U-11. The tests were carried out together with SU-85. Because of breakages of SU-122-III (such index has received new SP before tests), from tests it was removed.You can recornize the vehicle from the SU-122 because his bolt gun mask, meanwhile the SU-122 have an blocky gun mask. But be careful, the next variant was the same variant but with a commander cupola.
This version was just the same version like above, the SU-122-III but from 1944. It had - against the 1943 model - an commander cupola on the right side of the tank. Just like the 1943 model, it had never saw service on the front during World War Two.