The AR-15, or "ArmaLite" 15 rifle was invented by American firearms manufacturer ArmaLite in 1956 under the guidance of former Marine and Army Ordinance technician Eugene Stoner.
German infantry-weapons developer Hugo Schmeisser designed the first mass-produced assault rifle, the Sturmgewehr 44, for Nazi military use during World War II. Various countries subsequently created their own assault rifles, including the Soviet AK-47 and the British EM-2.
Originally a fully automatic weapon, the AR-15 was the standard-issue rifle for American troops during the Vietnam War, where it was known as the M-16. A semi-automatic version was later made available to the public.