During the Soviet offensive of the winter of 1943 it made apparition in the frontline a new model of Russian armored vehicle, characterized by lacking turret and having the cannon installed in a casemate. This vehicle, denominated SU-85 (Samochodnia Ustanovka 85 or Self-Propelled Cannon 85), soon earned the sympathy of its crews and the respect of the enemy. It was product of the work of a group of investigators on which stood out the engineers Makonin, Gorlick and Troyanov, which in a rather short timespan had adopted the principle of the German assault cannons, which so much success had had.

It would be improper to define this vehicle as an armored artillery piece, for its cannon was exactly the same that the one installed in the medium tank T-34/85. On the other hand, the SU-85 had not been exclusively developed to perform anti-tank functions, as the ISU-152. It was actually a true assault cannon, more alike to the German Sturmgeschutz than to the Italian Ansaldo Fiat 75/18, and able to face in equality of conditions the enemy tanks of its time. Also, it could follow the infantry, and because of this it was fitted with large handholds so, following a Soviet use, the soldiers could clamber onto the vehicle, remaining in the center of the combat and effectively fighting against static and mobile targets.

To develop this weapon, the projectors thought appropriate, both because of how practical it was from a logistical standpoint as to achieve a faster production, to use the chassis and mechanics of the T-34, designing a new superstructure that allowed the installation of the artillery piece and the crew. This way the profile of the tank was lower and less vulnerable to the enemy shots. The cannon, originally the 85-millimeter anti-aircraft piece M 1939, could rotate 20 degrees at both sides. In 1944 it was replaced by the new D5 S85A M 1944, of improved ballistic characteristics.

In total, during the war were built little more than 500 exemplars of the SU-85, very small number considering the huge amount of tanks and armored vehicles in general built in the Soviet Union, but still justified. Because despite being more compact and less vulnerable to enemy fire, it had the deficiency of not being able to quickly cover the 360 degrees. Later, due to the robustness of its construction, the projectors decided to install cannons of larger caliber. So it was created the SU-100, which remained in active service with the Soviet Army until 1957.

The importance of the SU-85, despite the limited production and the short life in active service, is indubitable. Actually it was the first exponent in a series of self-propelled vehicles and, as such, it served as testing bench for the rest of them. When in 1944 it was decided to retire it from active service, for it was being carried out the production of the new models armed with the new cannon M 1944, it was given to the armies of the countries which later would become client states of the Soviet Union.