Medium tank is a classification of tanks, particularly prevalent during World War II which represented a compromise between the mobility oriented light tanks and the armour and armament oriented heavy tanks. The most widely produced, cost effective and successful tanks of World War II (the Soviet T-34, the American Sherman tank, the Japanese Type 97 and the German Panzer IV) were all medium tank designs, and the success of the concept would later lead to the development of later generations of medium tanks such as the Chieftain. Many of the medium tanks lines became what are called main battle tank in most countries.