Original Thompson Sub Machine Guns for sale at International Military Antiques, Inc. The Thompson was an American submachine gun, invented by John T. Thompson in 1919, 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 "TSMG", the "Tommy Gun", the "Trench Broom", the "Trench Sweeper", the "Chicago Piano", the "Chicago Typewriter", and the "Chopper". The Thompson was favored by soldiers, criminals and police alike for its ergonomics, compactness, large .45 ACP cartridge, reliability, and high volume of automatic fire and among civilian collectors for its historical significance.