The
M1911 is a
single-action,
semi-automatic, magazine-fed,
recoil-operated pistol chambered for the
.45 ACP cartridge. It served as the standard-issue
sidearm for the
United States Armed Forces from 1911 to 1986. It was first used in later stages of the
Philippine–American War, and was widely used in
World War I,
World War II, the Korean War, and the
Vietnam War. The pistol's formal designation as of 1940 was
Automatic Pistol, Caliber .45, M1911 for the original model of 1911 or
Automatic Pistol, Caliber .45, M1911A1 for the M1911A1, adopted in 1924. The designation changed to
Pistol, Caliber .45, Automatic, M1911A1 in the Vietnam era.