In the 1920s an American could order a Thompson submachine gun by mail for $200 and have it shipped to the front door. That was never the plan. Brigadier General John T. Thompson designed the weapon in 1918 to break the stalemate of trench warfare, giving a single soldier the firepower of a machine gun. A friction-based mechanism called the Blish lock forced him to settle for the .45 ACP pistol cartridge, and the war ended two days before the first prototypes could be shipped to Europe.

With no military buyer, the Auto-Ordnance company sold to anyone who would pay. This episode follows the gun through the coal wars of West Virginia, shipments smuggled to the Irish Republican Army, and the Prohibition gangs that made it the Chicago typewriter. It then tracks an unlikely return to respectability through the postal service and the Marine Corps, and a wartime redesign that turned an expensive showpiece into a cheap mass-produced tool carried by Allied troops around the world.

• At a 1919 board meeting the project, first dubbed the Annihilator, was renamed the Thompson submachine gun, the first weapon marketed under that term.
• Its first recorded combat use came in West Virginia in June 1921, where state police, coal companies, and striking miners all bought them.
• The Postal Inspection Service bought around 200 Thompsons in 1926 to stop mail robberies, which put the gun in the hands of Marines guarding shipments.
• Soldiers disliked the 50-round drum magazine because it was heavy, rattled on patrol, and was slow to load, so the military switched to box magazines.
• Dropping the Blish lock and other refinements cut the price from about $209 in 1939 to $45 by 1944, and more than 1.5 million were built for World War II.