The SU-85, SU-100 and SU-122 were Soviet self-propelled guns used during World War II, based on the chassis of the T-34 medium tank
About this creation
Since the SU-85, SU-100 and SU-122 are essentially the same thing just with different guns, I decided to put them all in one page.
Early in World War II, Soviet tanks such as the T-34 and KV-1 had enough firepower to destroy any German tank then available. However, in the fall of 1942, Soviet forces encountered the new German Tiger tank, with armor too thick to be penetrated by the 76.2 mm guns used in the T-34 and KV tanks at a safe range. By spring 1943, the Soviets had also received reports of the new Panther tank, although the Panther was not seen in combat until July 1943, during the battle of Kursk. This new generation of German vehicles meant the Red Army needed a new and more powerful tank destroyer. Thus, the SU-85 was conceived.
The SU-85 was a modification of the earlier SU-122 self-propelled howitzer, essentially replacing the 122 mm M-30S howitzer of the SU-122 with a D-5T high-velocity 85 mm antitank gun. The vehicle was small with good mobility. The trade-off was its relatively light armor.
The SU-100 was an improvement on the SU-85, mounting a larger and much longer 100mm D-10S gun. It was used extensively during the last year of World War II and saw service for many years afterwards with the armies of Soviet allies around the world.
The SU-100 quickly proved itself to be able to knock out any German tank, save for the King Tiger, from a distance of 1500m. Due to its capabilities, Soviet soldiers gave it the affectionate nickname "Pizdets vsemu" ("F*cking end to everything").
The basis for the SU-85 and SU-100, the SU-122 was an assault gun, not a tank destroyer. It mounted a 122mm M-30S howitzer
The Soviet High Command became interested in assault guns following the success of the German StuG III. Assault guns had some advantages over tanks. The lack of a turret made them cheaper to produce. They could be built with a larger fighting compartment and could be fitted with bigger and more powerful weapons on a given chassis. However, assault guns could only aim their weapons by turning the entire vehicle, and were thus less suited for close combat than tanks.