The submachine-gun is a compact automatic weapon firing pistol ammunition, designed for short-range assault and close-quarter fighting and was first used by the German Army in 1917.

Inspired by the sub-machine guns used by the Germans in the First World War General John T. Thompson designed what became known as the Tommygun. The gun was not ready in time for the war but was used in the 1920s by American gangsters.

The US Marines began using the Tommygun in 1928 and so did the British Army in the early stages of the Second World War. The United States Army also began to use them and by August 1941, had ordered 318,900 of these guns. Although heavier than other submachine-guns, it was considered the most reliable available.