Following the assassination of Gemayel in September 1982 , Israel 's position in Beirut became untenable and the signing of a peace treaty became increasingly unlikely . Outrage following Israel 's role in the Phalangist-perpetrated Sabra and Shatila massacre , of mostly Palestinians and Lebanese Shiites , and Israeli popular disillusionment with the war would lead to a gradual withdrawal from Beirut to the areas claimed by the self-proclaimed Free Lebanon State in southern Lebanon ( later to become the South Lebanon security belt ) , which was initiated following the 17 May Agreement and Syria 's change of attitude towards the PLO . After Israeli forces withdrew from most of Lebanon , the War of the Camps broke out between Lebanese factions , the remains of the PLO and Syria , in which Syria fought its former Palestinian allies . At the same time , Shi'a militant groups began consolidating and waging a low-intensity guerrilla war over the Israeli occupation of southern Lebanon , leading to 15 years of low-scale armed conflict . The Lebanese Civil War would continue until 1990 , at which point Syria had established complete dominance over Lebanon
Sabra and Shatila massacre
Sabra and Shatila massacre
1982 Lebanon War