The British Army introduced the first factory-built white phosphorus grenades in late 1916 during the First World War. During the war, white phosphorus mortar bombs, shells, rockets, and grenades were used extensively by American, Commonwealth, and, to a lesser extent, Japanese forces, in both smoke-generating and antipersonnel roles. The Royal Air Force based in Iraq also used white phosphorus bombs in Anbar Province during the Iraqi revolt of 1920.