After the attack on Pearl Harbor, during World War II, Butaritari and Tarawa, and others of the Northern Gilbert group, were occupied by Japan from 1941 to 1943. Betio became an airfield and supply base. The expulsion of the Japanese military in late 1943 involved one of the bloodiest battles in US Marine Corps history. Marines landed in November 1943 and the Battle of Tarawa ensued. Ocean Island, where were the headquarters of the colony, was bombed, evacuated and occupied by Japan in 1942 and only freed in 1945, after the massacre of all but one Banabans by the Japanese forces. Funafuti hosted then the provisional headquarters of the colony from 1942 to 1946, when Tarawa returned to host the headquarters, replacing Ocean Island.