The SU-76 (Samokhodnaya Ustanovka 76) was a Soviet light self-propelled gun used during and after World War II. The SU-76 was based on a lengthened version of the T-70 light tank chassis and armed with the 76 mm divisional gun M1942 (ZiS-3). Its quite simple construction and multipurpose combat role made it the second most produced Soviet armoured fighting vehicle of World War II, after the T-34 medium tank. History Design of the SU-76 began in November 1942, when the State Defense Committee (GKO) ordered the construction of infantry support self-propelled guns armed with the ZIS-3 76.2 mm divisional field gun and the M-30 122 mm howitzer. The T-70 light tank chassis was chosen for mounting the ZIS-3 gun, and was lengthened, adding one road wheel per side, to facilitate better gun mounting. The vehicle was not completely enclosed by armour, the rear roof and upper rear side exposed. The SU-76 was adopted by the GKO on December 2, 1942. The first batch of SU-76s (25 units) was manufactured by January 1, 1943 and sent to the self-propelled artillery training center. At the end of January, the first two self-propelled artillery regiments of a mixed organization (1433rd and 1434th) were sent to the Volkhov Front to participate in breaking the blockade of Leningrad. In March 1943, two more regiments were formed - the 1485th and 1487th, which participated in the battles on the Western Front (USSR). However, already after 10 days of military operation in the winter of 1943, most of the SU-76s were out of order due to breakdowns in gearboxes and main shafts. It became obvious that the SU-76 transmission had a design defect, which was the parallel installation of two twin engines that worked on a common shaft. Moreover, the maximum value of the resonant frequency accounted for the most intense mode of operation of the engines (driving in 2nd gear off-road), which led to their rapid failure. Therefore, on March 21, 1943, the production of the SU-76 was suspended. A total of 560 units were made. A more reliable vehicle, the SU-15, came about as a result of a competition for a light assault SPG armed with a 76.2 mm divisional gun. GAZ and Plant No. 38 took part in the competition. Two chief designers at the GAZ plant, N. A. Astrov and A. A. Lipgart, changed the power-plant arrangement to that of the T-70 light