The rational behind the First Lebanon War was as a response to the assination of the  Israeli ambassador to the U.K, Mr. Shlomo Argov, which was carried out on June 3rd, 1982, by Palestinian terrorists.

Abu Nidal's men supported by Iraq were against the Fatah regime.

Inspite of the cease-fire agreement in June, 1981, the PLO in Lebanon became more established and intimidating.

Terrorist attacks originating from the north and missile attacks on the Galilee settlements, preceded the First Lebanon War.

Targets changed during the War. Menachem Begin was prime minister at the time, Arik Sharon  was Defence Minister, and Raful, Chief of Staff. They of course agreed that the IDF forces should move into Lebanon.

At first it was thought that the operation should be limited. Later the Israeli Army reached Beirut and besieged the Fatah forces and the head of the snake, PLO, headed by Arafat within Beirut.

The war ended when the Fatah forces left Lebanon and Israel continued the siege.