September 1970 is known as Black September in Arab history. In September 1970, King Hussein moved to quash an attempt by armed Palestinian insurgents to overthrow his monarchy. The violence resulted in civilian casualties on both sides. Armed conflict lasted until July 1971 ending only when remaining Palestinian insurgents were surrounded in the Ajloun-Jarash mountains, finally surrendered to the Jordan army and were expelled from the country.' In October 1970, the Ba'athist regime in neighboring Syria had attempted to intervene in support of the Palestinians by sending an armoured column into the north of Jordan. Jordanian ground and air forces were able to halt this advance and a combination of international political pressure and discord within the Syrian military led to a Syrian retreat.