The Israeli army launched a massive military incursion into Lebanon in the summer of 1982. Operation "Peace for Galilee" was intended to wipe out Palestinian guerrilla bases near Israel's northern border, although Defence Minister Ariel Sharon pushed all the way to Beirut and expelled the PLO from the country.
The invasion began on 6 June, less than two months after the last Israeli troops and civilians were pulled out of Sinai under the 1979 treaty with Egypt. The action was triggered by the attempt on the life of Israeli ambassador to London Shlomo Argov by the dissident Palestinian group Abu Nidal.
Israeli troops reached Beirut in August. A ceasefire agreement allowed the departure of PLO fighters from Lebanon, leaving Palestinian refugee camps defenceless.
As Israeli forces gathered around Beirut on 14 September, Bashir Gemayel, leader of the Christian Phalange militia, was killed by a bomb at his HQ in the capital. The following day, the Israeli army occupied West Beirut.
From 16 to 18 September, the Phalangists - who were allied to Israel - killed hundreds of Palestinians in the Sabra and Shatila refugee camps as they were encircled by Israeli troops in one of the worst atrocities of nearly a century of conflict in the Middle East. Mr Sharon resigned from his post as defence minister after a 1983 Israeli inquiry concluded that he had failed to act to prevent the massacre.