The T-54 and T-55 tanks were a series of main battle tanks designed in the Soviet Union. The first T-54 prototype appeared in March 1945, just before the end of the Second World War. The T-54 entered full production in 1947 and became the main tank for armored units of the Soviet Army, armies of the Warsaw Pact countries, and others. T-54s and T-55s were involved in many of the world's armed conflicts during the late 20th and early 21st century.
The T-54/55 series eventually became the most-produced tank in history. Estimated production numbers for the series range from 86,000 to 100,000.
T-54/55 tanks were replaced by the T-62, T-64, T-72, T-80, and T-90 in the Soviet and Russian Armies, but many remain in use by up to 50 other armies worldwide, some having received sophisticated retrofitting.
Soviet tanks never directly faced their NATO Cold War adversaries in Europe. However, the T-54/55's first appearance in the west in 1960 spurred the United States to develop the M60.
In 1961, development of improved NBC protection systems began. The goal was to protect the crew from fast neutrons; adequate protection against gamma radiation was provided by the thick armour and a PAZ basic NBC protection system.
The POV plasticized lead antiradiation lining was developed to provide the needed protection. It was installed in the interior, requiring the driver's hatch and the coamings over the turret hatches to be noticeably enlarged. This liner had the added benefit of protecting the crew from fragments of penetrated armour.
The tank was equipped with a full PAZ/FVU chemical filtration system. The coaxial 7.62 mm SGMT machine gun was replaced by a 7.62 mm PKT machine gun. The hull was lengthened from 6.04 m to 6.2 m. The hull machine gun was removed, making space for six more main gun rounds. These changes increased the weight of the vehicle to 38 tonnes.
The design work was done by OKB-520 design bureau of Uralvagonzavod under the leadership of Leonid N. Kartsev. The T-55A served as the basis for the T-55AK command tank.