ZiS-2 57mm is a Soviet Anti-tank unit in Steel Division II.
Dating back to 1940, the ZiS-2 started its life as a counter for expected Nazi heavily armored tanks. Developed by V.G. Grabin's design bureau at the No. 92 Artillery Factory (the aforementioned ZiS, or Zavod imeni Stalina, Stalin's Factory), it was an automatic-action anti-tank gun firing a high velocity 57mm round capable of penetration up to 90mm of armor. Production began in June 1941, shortly before the Nazi invasion of the Soviet Union, and stopped in December, after it was discovered that the gun was too good at its job and routinely overpenetrated, going through the relatively lightly armored Panzers I through IV of the time. Only 371 were produced up to that point.
However, it would have the last laugh. The appearance of the Panther and Tiger tanks in 1943 radically changed the situation. The ZiS-3 76.2mm divisional gun and 45mm anti-tank guns used by the Soviets suddenly became incapable of dealing with the armored threats and the ZiS-2 was once again put into production, rolling off the production lines until 1945. 9 645 units were produced by the time production was shuttered at the end of the war. Although higher caliber anti-tank guns were deployed by that time, the ZiS-2's light weight and high rate of fire (on the order of 25 rounds per minute) resulted in it being used by Soviet airborne units for decades more, while various countries around the world either retained the ZiS-2 in reserve or used it in their armies.