First phase 1975–77[edit]
Sectarian violence and massacres[edit]
Throughout the spring of 1975, minor clashes in Lebanon had been building up towards all-out conflict, with the Lebanese National Movement (LNM) pitted against the Phalange, and the ever-weaker national government wavering between the need to maintain order and cater to its constituency. On the morning of 13 April 1975, unidentified gunmen in a speeding car fired on a church in the Christian East Beirut suburb of Ain el-Rummaneh, killing four people including two Maronite Phalangists. Hours later, Phalangists led by the Gemayels killed 30 Palestinians traveling in Ain el-Rummaneh. Citywide clashes erupted in response to this "Bus Massacre". The Battle of the Hotels began in October 1975, and lasted until March in 1976.
On 6 December 1975, a day later known as Black Saturday, the killings of four Phalange members led Phalange to quickly and temporarily set up roadblocks throughout Beirut at which identification cards were inspected for religious affiliation. Many Palestinians or Lebanese Muslims passing through the roadblocks were killed immediately. Additionally, Phalange members took hostages and attacked Muslims in East Beirut. Muslim and Palestinian militias retaliated with force, increasing the total death count to between 200 and 600 civilians and militiamen. After this point, all-out fighting began between the militias.
In a vicious spiral of sectarian violence, civilians were an easy target. On 18 January 1976 about 1,000 people were killed by Maronite forces in the Karantina Massacre, immediately followed by a retaliatory strike on Damour by Palestinian militias. These two massacres prompted a mass exodus of Muslims and Christians, as people fearing retribution fled to areas under the control of their own sect. The ethnic and religious layout of the residential areas of the capital encouraged this process, and East and West Beirut were increasingly transformed into what was in effect Christian and Muslim Beirut. Also, the number of Maronite leftists who had allied with the LNM, and Muslim conservatives with the government, dropped sharply, as the war revealed itself as an utterly sectarian conflict. Another effect of the massacres was to bring in Yassir Arafat's well-armed Fatah and thereby the Palestine Liberation Organisation on the side of the LNM, as Palestinian sentiment was by now completely hostile to the Maronite forces.