John T. Thompson was an American inventor and military officer best known for developing the Thompson submachine gun, often referred to as the "Tommy Gun." Born in 1860, he designed this firearm during World War I, and it became famous for its use by both law enforcement and gangsters in the 1920s and 1930s. Thompson's invention was notable for its high rate of fire and effectiveness in close combat. The Thompson submachine gun played a significant role in shaping modern firearms and is still recognized today for its historical impact on both military and civilian use.