The Thompson Submachine Gun, often referred to as the "Tommy Gun," is a .45 caliber submachine gun that was designed by John T. Thompson in the early 20th century. It became famous during the Prohibition era in the United States, primarily used by gangsters and law enforcement. Its distinctive design features a wooden stock and a drum magazine, allowing for high-capacity fire. Introduced in 1921, the Thompson was known for its reliability and rate of fire, making it effective in close combat situations. It was utilized by various military forces during World War II and has since become an iconic symbol of the era, often appearing in films and popular culture.