Thompsom Submachine Gun a

The Thompson submachine gun is an American submachine gun that became infamous during the Prohibition era. It was a common sight of the time, being used by both law enforcement officers and criminals.[1] The Thompson was also known as: the "Tommy Gun", the "Trench Broom", the "Chicago Piano", the "Chicago Typewriter", and the "Chopper".[2][3][4][5][6]
The Thompson was favored by soldiers and civilians alike for its compactness, large .45 ACP cartridge, and high volume of automatic fire.

History and service

A Marine fires on a Japanese position using an M1A1 Thompson submachine gun during an advance on Okinawa in 1945.
The Thompson Submachine Gun was designed by General John T. Thompson, who was inspired by the trench warfare of World War I to develop a "one-man, hand-held machine gun", firing a rifle caliber round. While searching for a way to allow such a weapon to operate safely, Thompson came across a patent issued to John Bell Blish. Thompson found a financial backer, Thomas Fortune Ryan, and started the Auto-Ordnance Corporation in 1916 for the purpose of developing his weapon. The principal designers were Theodore H. Eickhoff, Oscar V. Payne, and George E. Goll. By late 1917, the limits of the Blish lock were discovered, and it had been found that the only cartridge currently in U.S. service suitable for use with the lock was the .45 ACP (Automatic Colt Pistol). The project was then titled "Annihilator I", and by 1918, most of the design issues had been resolved. However, the war ended before prototypes could be shipped to Europe.

At an Auto-Ordnance board meeting in 1919 to discuss the marketing of the "Annihilator", with the war over, the weapon was officially renamed the "Thompson Submachine Gun". While other weapons had been developed shortly prior with similar objectives in mind, the Thompson was the first weapon to be labeled and marketed as a "submachine gun".[7] Thompson intended the weapon as an automatic 'trench-broom' to sweep enemy troops from the trenches, filling a role the BAR had proved incapable of.[8] Coincidentally, this concept was adopted by German troops using their own submachine guns in concert with sturmtruppen tactics.[9]
The Thompson first entered production as the M1921. It was available to civilians, though its high price resulted in few sales. M1921 Thompsons were first sold in small quantities to the U.S. Post Office (to protect the mail from a spate of robberies[10]), followed by several police departments in the United States and minor international sales to various armies and constabulary forces, chiefly in Central and South America. The U.S. Post Office also gave Thompsons to the U.S. Marine Corps in 1922 when Marines were assigned to protect against mail robberies,[11] with the Marines putting them to use in the Banana Wars and in China.[12] It was popular with the Marines as a point-defense weapon for countering ambush by Sandinista guerrillas and led to the organisation of 4 man fire teams with as much firepower as a 9 man rifle squad. The major complaints against the Thompson were its weight, inaccuracy at ranges over 50 yards, and its lack of penetrating power, despite the powerful .45 cal ACP round it used. [13]
Thompsons were also acquired by the Irish Republican Army from supporters in the U.S. and were used in the latter stages of the Irish War of Independence and Civil War.

The Thompson achieved most of its early notoriety in the hands of Prohibition and Depression-era gangsters and in Hollywood films, most notably in the St Valentine's Day Massacre. It was often referred to as the "gun that made the twenties roar."[14]
Nationalist China also acquired a quantity for use against Japanese land forces, and eventually began producing copies of the Thompson in small quantities for use by its various armies and militias.