The M1 Thompson, commonly known as the Thompson submachine gun, is a .45 caliber firearm developed in the early 20th century. It was designed by John T. Thompson and became famous for its use during World War II and in the Prohibition era. The M1 variant was a simplified version, featuring a wooden stock and a 30-round magazine, making it easier to manufacture and more affordable. The Thompson submachine gun is often associated with law enforcement and gangsters in the 1920s and 1930s. Its distinctive design and high rate of fire contributed to its popularity in both military and civilian contexts. The M1 Thompson remains an iconic symbol of American firearms history, often featured in movies and media related to that era.