The SU-100 is a Soviet tank destroyer with a very long operating history. It saw service in the Red Army during the Second World War and in several countries in the following decades.
Its name in cyrillic is CY-100, acronym of Cамоходная Yстановка 100 ("Samokhodnaya Ustanovka 100"), that is "Self-Propelled Unit 100". The caliber of its main gun is 100 mm, hence the name.
The development started in 1944 as an update for the SU-85 tank destroyer, based in turn on the T-34 hull. Those tank destroyers replaced the turret of the tank with a casemate. This limited sensibly the traverse of the main armament, but it also allowed to mount a more powerful gun.
Respect to its predecessor, which used a 85 mm (3.3 in) gun, the SU-100 mounted thee powerful D-10S gun, with a caliber of 100 mm (3.94 in). Moreover, it improved its armor and it saw the addition of a commander cupola, which drastically improved its tactical effectiveness.
The SU-100 main weapon was capable of piercing from a long distance the thick frontal armour of the German Tiger and Panther tanks. On the other hand, it lacked a machine gun, so it had to rely on the support of infantry and other vehicle to defend itself from enemy soldiers.
The armor reached the thickness of 75 mm (2.95 in), but with a maximum slope of 55°, which increased a lot its protection. Its weight was about 31 metric tonnes (almost 70,000 lbs).
The crew consisted in commander, gunner, loader and driver, whereas the engine was a 38.8 liters V-12 diesel, with a power output of 500 hp. Thus, it could reach a speed of 48 km/h (30 mph) with a maximim range of 250 km (155 miles).
The mass production of the SU-100 started in September 1944. It saw service with the Soviets in the last phases of the Second World War, and was withdrawn in 1967. Many countries in Europe, Middle East, Eastern Asia and Africa, as well as Cuba, kept using them in the following years. Almost 5000 were built.
Examples of wars where it fought are the Suez Crisis in 1956, the Arab-Israeli Wars of 1967 and 1973 and the 1990s Yugoslavian Civil War. It is stiil in service in Vietnam and North Korea.