Tension along Israel's northern border increased in the course of 1981 following the lobbing of Katyusha rockets at Israeli settlements by terror organizations in southern Lebanon. A ceasefire declared in July 1981 was broken: the terrorists continued to carry out attacks against Israeli targets in Israel and abroad, and the threat to the northern settlements became unbearable. On June 3, 1982 terrorists shot Shlomo Argov, Israel's Ambassador to Britain. Three days later, on June 6, 1982, the IDF launched Operation Peace for the Galilee.
The War in Lebanon can be divided into two phases. The first was a conventional war, which lasted from June 6 to August 23, 1982, when the terrorists were expelled from Beirut. The second phase, which lasted for the next three years, was directed against the terrorists. At the beginning of the war, the IDF advanced along the shore, crossed the Awall River, went into Beirut, and then continued north through the Shouf Mountains along the flank of the main Syrian forces in the Beka'a Valley, threatening their rear as well as comminications between Beirut and Damascus.
The IAF's most stunning achievement in the war was the destruction of the Syrian SAM array in the Lebanese Beka'a Valley, within a matter of hours. This operation was accompanied by a massive air battle, in which 25 Syrian planes - most of them MiG-23s - were shot down. The Syrian air defense was effectively nonexistent from that day on.
The enlargement of the mission and the capture of Beirut signalled the transition to a long drawn-out war, which failed to achieve its ultimate purpose. A peace treaty with Lebanon was signed, but not ratified; the Christian government of fragmented Lebanon was too weak to prevail.
Daily ambushes against Israeli occupying forces increased, with a corresponding increase in casualties - 1,216 soldiers killed between 5 June 1982 and 31 May 1985. One of its first and most important victims was the national consensus. For the first time in the history of Israel not only was the conduct of war debated - for this there had been ample precedent - but the very justification of the war. Prime Minister Menahem Begin himself provided the watchword: a War of Choice, unlike all previous wars, which were perceived as dire necessities.
The failure of Operation Peace of Galilee to achieve its objective prevailed upon the new national coalition government, which took office in 1984, to withdraw forthwith from Lebanon. A token force was left behind, to help the citizens of south Lebanon to patrol the Security Zone - a narrow strip of territory adjacent to Israel's border, which was an essential tripwire for Israeli settlements, some of which are located next to the border.
Quoted in part from "The Arab-Israeli Wars" by Netanel Lorch