The Thompson is 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 "Tommy Gun", "Trench Broom", "Trench Sweeper", "Chicago Typewriter", "Chicago Piano", "Chicago Style", "Chicago Organ Grinder", and "The Chopper".
In 1938, the Thompson submachine gun was adopted by the U.S. military, serving during World War II and beyond.
There were two military types of Thompson SMG:
- The M1928A1 had provisions for box and drum magazines. It had a Cutts compensator, cooling fins on the barrel, employed a delayed blowback action and its charging handle was on the top of the receiver.
- The M1 and M1A1 had a barrel without cooling fins, a simplified rear sight, provisions only for box magazines, employed a straight blowback action and the charging handle was on the side of the receiver. Over 1.5 million military Thompson submachine guns were produced during World War II