The Thompson submachine gun (nicknamed the Thompson) is an American submachine gun, invented by John T. Thompson in 1918, that became infamous during the Prohibition era. It was a common sight in the media of the time, being used by both law enforcement officers and criminals. The Thompson was also known informally as: the "Tommy Gun", "Trench Broom", "Trench Sweeper", "Chicago Typewriter", "Chicago Piano", "Chicago Style", "Chicago Organ Grinder", and "The Chopper"


The Thompson was favored by soldiers, criminals, police and civilians alike for its large .45 ACP cartridge, accuracy, and high volume of automatic fire. It has since gained popularity among civilian collectors for its historical significance.

The Thompson Submachine Gun was developed by General John T. Thompson who originally envisioned an auto rifle (semi-automatic rifle) to replace the bolt action service rifles then in use. While searching for a way to allow such a weapon to operate safely without the complexity of a recoil or gas operated mechanism, Thompson came across a patent issued to John Bell Blish in 1915 based on adhesion of inclined metal surfaces under pressure. Thompson found a financial backer, Thomas F. Ryan, and started the Auto-Ordnance Company in 1916 for the purpose of developing his auto rifle. It was primarily developed in Cleveland, Ohio.[14] The principal designers were Theodore H. Eickhoff, Oscar V. Payne, and George E. Goll. By late 1917, the limits of the Blish Principle were discovered: rather than working as a locked breech, it functioned as a friction-delayed blowback action. It was found that the only cartridge currently in U.S. service suitable for use with the lock was the .45 ACP round. Thompson then envisioned a "one-man, hand-held machine gun" in .45 ACP as a "trench broom" for use in the ongoing trench warfare of World War I. Payne designed the gun itself and its stick and drum magazines. The project was then titled "Annihilator I" and by 1918, most of the design