The M1911 is a single-action, semi-automatic pistol chambered for the .45 ACP cartridge, and served as the standard-issue sidearm for the United States military from 1911 to 1985. It was widely used from the First World War all the way up to the Vietnam War. Modern M1911 variants are still in use by some units within the U.S. Army Special Forces, the U.S. Navy and U.S. Marine Corps. The Automatic Pistol, Caliber .45, M1911 was designed by John Browning, and is the best known of his designs to use the short recoil principle in its basic design. The design was widely copied, and this operating system rose to become the most renowned type of the twentieth century. In total, the United States purchased around 2.7 million M1911 and M1911A1 pistols in military contracts during its service life. Created in 1940, this field manual reveals a great deal about the M1911's design and capabilities. Intended as a manual for those charged with operation, it details many strategies for achieving outstanding marksmanship. Originally labeled restricted, this manual was declassified long ago and is here reprinted in book form. Care has been taken to preserve the integrity of the text."