PLO military forces constitute another potential threat to the stability of the Syrian regime. Hostilities between Syria and Yasir Arafat and the PLO's Al Fatah faction intensified in May 1983 when armed rebellion against Arafat's leadership broke out. With Syrian approval, Abu Musa-led Fatah dissidents overran Al Fatah supply centers in Damascus in late May 1983. In June, July, and early August 1983, Syrian forces also actively supported the anti-Arafat forces fighting in the Biqa Valley and succeeded in driving the Arafat loyalists north into Tripoli. On June 24 Arafat was expelled from Damascus. In Syrian-dominated areas of Lebanon, Syrian officials also confiscated PLO arms and depots. With Syria's active support, Palestinian factions opposed to Arafat's rule, i.e., the Abu Nidal organization, assassinated high-ranking PLO officials in the Middle East and Western Europe. Syria also sponsored the Damascus-based Palestine National Salvation Front, an anti-Arafat coalition, consisting of such groups as the Popular Front for the Liberation of Palestine (PFLP) and the Democratic Front for the Liberation of Palestine (DFLP). Although many PLO forces had been expelled from Syria, a PLA brigade, with a force of some 4,500, was still stationed there however, it was carefully watched, infiltrated by Syrian security officials, and dependent on Syria for arms and supply routes. During the mid-1980s these measures were effective in preventing any organized PLO insurgency against the Assad regime, but the potential for such a threat remained in early 1987, when many pro-Arafat PLO fighters had begun moving back to Lebanon.

Data as of April 1987