The SU-1 was developed in 1931-32 at the Lenningrad plant based on the chassis of the T-26 tank. It is considered the world's first self propelled gun. The design featured a single superstructure mounting a 76.2mm Model 1927 regimental gun with a shortened recoil. Secondary armament was provided by two 7.62mm DT machine guns. The SU-1 was crewed by three men.