The M1911 is a single-action, semi-automatic, magazine-fed, recoil-operated pistol chambered for the .45 ACP cartridge, which served as the standard-issue sidearm for the United States armed forces from 1911 to 1985. It was widely used in World War I, World War II, the Korean War, and the Vietnam War. The M1911 is still carried by some U.S. forces.
Designed by John Browning, the M1911 is the best-known of his designs to use the short recoil principle in its basic design. The pistol was widely copied, and this operating system rose to become the preeminent type of the 20th century and of nearly all modern centerfire pistols.