Christian militias such as the Kataeb Regulatory Forces and the Guardians of the Cedars began attacking Palestinian refugee camps shortly after the war began due to the PLO 's support for Muslim and leftist factions . On January 18 , they forcibly took control of the Karantina district , resulting in the Karantina Massacre . The Christian forces were initially leery of escalating PLO involvement in the war , but Karantina was inhabited partly by Lebanese Muslims and was located along the main road they needed to resupply their positions in Beirut , so it was considered a legitimate target . However , the PLO joined Muslim militias in retaliating for the Karantina Massacre by massacring the Christian population of Damour
massacring
Damour massacre
Siege of Tel al-Zaatar