The production of the SU-100 has begun in the early spring of 1944, but the production rates have been slowed down due to an unavailability of 100mm D-10S guns. By this time, the ChKZ produced SPG called SU-85. However, a stronger tank destroyer was need. Soon to be launch was a new series of self-propelled guns, known as the SU-122P, which was to replace the SU-100.
The SU-122P was a little different from the SU-100. Although both self-propelled guns were based on the T-34-85 chassis and shared the same fighting compartment and cabin, the SU-122P, as the name implies, was fitted with the 122-mm D-25S gun with a muzzle brake.
In September 1944, the self-propelled gun prototype was built and sent sent for trials. Despite the success, the order for mass production has not been approved. The main reason for dissatisfaction was that the D-10C gun was much better than the 122mm gun in terms of armor penetration and rate of fire, and even had a stronger impact. Production of SU-122P has not been renewed until the end of the war and after. However, later a new ISU serie of tank destroyers was designed. Amongst them was the ISU-122, the successor of the SU-122P and with the same gun. Also, the IS-2 shared the same chassis as the ISU-122 and the same D-25S gun.
Unfortunately, it was removed from the mod in version 0.55 along with the only map it was presented on - Spurning Fate.