The United States Army on March 29, 1911, adopted arguably the greatest combat pistol in history. The M1911 is a single-action, semi-automatic, magazine-fed, recoil-operated pistol chambered for the .45 ACP cartridge. 

The ubiquitous M1911 served as the standard-issue sidearm for the United States Armed Forces for over 75 years, from 1911 to 1986. The pistol, commonly known by GIs as the “45” served in World War I, World War II, the Korean War, the Vietnam War, and the Global War on Terror — indeed, some Special Operations units still carry the 1911

The government purchased about 2.7 million M1911/M1911A1 .45 pistols during its lifetime as the official sidearm of the military. It was eventually replaced by the Beretta M9, 9mm pistol. However, some specialized military and law enforcement units still carry either the M1911A1 or a variant of it.