M2 light tank
The M2 light tank, officially Light Tank, M2, was an American light tank of the interwar period which saw limited service during World War II. The most common model, the M2A4, was equipped with one M5 gun and five .30 cal M1919 Browning machine guns. It was originally developed from the prototype T2 light tank built by the Rock Island Arsenal, which had a Vickers-type leaf spring suspension. The suspension was replaced by the superior vertical volute system in the T2E1 series of 1935. This was put into production with minor modifications as the M2A1 in 1936, with ten produced. The main pre-war version was the M2A2, with 239 produced, becoming the main tank of the United States Army during the interwar period. The Spanish Civil War showed that tanks armed only with machine guns were ineffective. This led to the M2A4 with a 37 mm gun as the main armament. A total of 375 were delivered, the last ten as late as April 1942. The tank's only combat service was with the United States Marine Corps' 1st Tank Battalion in 1942 during the Pacific War. While some sources claim that the M2A4 saw action with British Army tank units in the Burma campaign against the Imperial Japanese Armed Forces, historian Mike Green states that the tanks were never issued to combat units. The M2A4 light tank led to the development of the M3 Stuart light tank and the M4 Tractor artillery prime mover, the former of which saw widespread use throughout World War II. US Army infantry tank design started with the light tank, T1 during the 1920s, which developed into a series of experimental designs which did not enter production. The T2 concept, starting five years later, incorporated several design lessons from the T1, but used a new suspension system copied from the British Vickers six-ton tank. The first prototype was delivered in 1933. The Defense Act of 1920 had defined tanks to be used in support of the infantry. Through the 1920s a number of theorists outlined an independent role for the tank that required it to move at high speed into the rear areas, a modern version of the cavalry.