2A19 or T-12 is a Soviet-designed 100-mm anti-tank gun. It was the first anti-tank gun to adopt a smoothbore barrel, and to introduce modern armor piercing shot, like the APFSDS. It uses long projectiles that are more powerful than its caliber suggests. The T-12 served as the primary towed anti-tank artillery in the Soviet and Bulgarian armies from the early 1960s to the late 1980s.The T-12 was designed by the construction bureau of the Yurga Machine-Building Plant as a replacement for the BS-3 100 mm gun. The first serial examples were produced in 1955, but the T-12 entered service only in 1961. Its special feature was the use of a smoothbore gun. The T-12 was typically deployed in the anti-tank units of armored and motor rifle regiments to protect flanks against counter-attacks during rapid advances.[2]In 1971, a new variant was introduced, T-12A or MT-12 “Rapira” (2A29). This has the same barrel, but has a redesigned carriage and gun shield. This allows the MT-12 to be towed by the MT-LB, giving greater mobility. The 2A29R “Ruta” or MT-12R is an MT-12 version with a radar system. From 1981, the gun could fire the laser beam-riding guided missile 9M117 Kastet (weapon system 9K116) and carried the new designator 2A29K “Kastet” or MT-12K.By the mid-1990s, modern western tanks’ frontal armor protection could no longer be penetrated by a 100 mm gun. The 100 mm caliber ammunition had reached the limits of what could be achieved with it. For a static anti-tank that cannot move to attack the sides of an opponent this is extra problematic. Today, the T-12 is applied mostly in the role of ordinary artillery, using FRAG-HE shells. The T-12 was planned to be superseded by the 2A45 Sprut-B 125 mm smooth bore anti-tank gun.