The T-34 was a Soviet medium tank produced from 1941 to 1958. It is widely regarded to have been the world's best tank when the Soviet Union entered World War II, and although its armor and armament were surpassed by later tanks of the era, it is credited as the war's most effective, efficient and influential design. First produced at the KhPZ factory in Kharkov (Kharkiv, Ukraine), it was the mainstay of Soviet armoured forces throughout World War II, and widely exported afterwards. It was the most-produced tank of the war, and the second most-produced tank of all time, after its successor, the T-54/55 series. A 1996 publication showed that the T-34 was still in service with twenty-seven countries.
The T-34 was developed from the BT series of fast tanks, and was intended to replace both the BT-5 and BT-7 tanks and the T-26 infantry tank in service (Zaloga & Grandsen 1984:66, 111). At its introduction, it was the tank with the best balanced attributes of firepower, mobility, and protection in existence, although initially its battlefield effectiveness suffered from the unsatisfactory ergonomic layout of its crew compartment, lack of radios and poor tactical employment. The two-man turret crew arrangement required the commander to also serve as the gunner, an arrangement common to most Soviet tanks of the day; this proved to be inferior to the German arrangement of three men (commander, gunner and loader).
The design and construction of the tank were continuously refined during the war to improve effectiveness and decrease costs, allowing steadily greater numbers of tanks to be fielded. In early 1944, the improved T-34-85 was introduced, with a more powerful 85 mm gun and a three-man turret design. By the war's end in 1945, the versatile and cost-effective T-34 had replaced many light and heavy tanks in service, and accounted for the majority of Soviet tank production. Its evolutionary development would lead directly to the T-54/55 series of tanks, built until 1981 and still operated today.