The layout of the T-54 is conventional, with the main armament comprising a 100mm rifled gun. The T-54 has been used more than any other tank since the Second World War. It is intended for combat actions involving tanks, combat vehicles, armored personnel carriers and other armored enemy targets. The T-55 combines a high velocity gun with exceptional long-range endurance. The T-55 has a fully tracked, five-road-wheeled chassis with a low-silhouetted hull and a dome-shaped turret. The T-54 series tanks first appeared in 1949 as replacements for the T-34 tank of World War II. The first T-54 prototype was completed in 1946 with first production beginning in 1947. The T-54 was continuously improved and modified, and, when sufficient changes had been made, the tank was re-designated T-55. The T-55 was introduced in 1958 and incorporates all the refinements and improvements of the fully developed T-54 series without being radically different in design or appearance. The T-55A appeared in the early 1960s. Production continued in the Soviet Union through 1981 and was also undertaken in China (as the Type 59), Czechoslovakia and Poland. Large numbers are still in service, although by the 1980s the T-54/55 had been replaced by the T-62, T-64, and T-72 as the primary main battle tanks in first-line Soviet tank and motorized rifle units. Used in the invasion of Hungary in 1956, Czechoslovakia in 1968, and Syria in 1970, it was the main Arab tank in the 1967 and 1973 wars with Israel. During the 1970s, the T-54 saw combat in Vietnam, Cambodia, and Uganda.