On June 6 , 1982 , the Israel Defense Forces ( IDF ) initiated Operation " Peace for Galilee " and invaded Lebanon in order to create a 40 km buffer zone between the PLO and Syrian forces in Lebanon and Israel . The Israeli invasion was tacitly approved by the U.S. , and the U.S. provided overt military support to Israel in the form of arms and materiel . The U.S. ' support for Israel 's invasion of Lebanon taken in conjunction with U.S. support for Lebanese President Bachir Gemayel and the Lebanese Armed Forces ( LAF ) alienated many . Bachir Gemayel was the legally elected president , but he was a partisan Maronite Christian and covert associate of Israel . These factors served to disaffect the Lebanese Muslim and Druze communities . This animosity was made worse by the Phalangist , a right-wing , largely Maronite-Lebanese militia force closely associated with President Gemayel . The Phalangist militia was responsible for multiple , bloody attacks against the Muslim and Druze communities in Lebanon and for the 1982 atrocities committed in the PLO refugee camps , Sabra and Shatila by Lebanese Forces ( LF ) , while the IDF provided security and looked on . The Phalangist militia 's attacks on Sabra and Shatila were purportedly a response to the September 14 , 1982 , assassination of President-elect Bachir Gemayel . Amine Gemayel , Bachir 's brother , succeeded Bachir as the elected president of Lebanon , and Amine continued to represent and advance Maronite interests
Sabra and Shatila
Sabra and Shatila massacre
1983 Beirut barracks bombings