In 1975, following increasing sectarian tensions, largely boosted by Palestinian militant relocation into South Lebanon, a full-scale civil war broke out in Lebanon. The Lebanese Civil War pitted a coalition of Christian groups against the joint forces of the PLO, left-wing Druze and Muslim militias. In June 1976, Lebanese President Elias Sarkis asked for the Syrian Army to intervene on the side of the Christians and help restore peace. In October 1976 the Arab League agreed to establish a predominantly Syrian Arab Deterrent Force, which was charged with restoring calm.