According the Nachik Navot, then-head of Mossad: [h/t to Bryan Atinsky]
http://www.haaretz.com/weekend/week-s-end/just-a-tool-in-the-war-machine-1.316342
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Navot says prime minister Menachem Begin was ready and waiting for the war. "Begin led the way to war because he was in great distress after Camp David," he said. "He understood that an autonomy agreement [as called for in Israel's 1979 peace treaty with Egypt] would lead to a Palestinian state. So he wanted to go to war in order to strike a blow at the PLO and to liquidate the state-within-a-state that the Palestinians carved out for themselves in Lebanon, in the hope that this would project onto the territories and that the concept of [Palestinian] autonomy would not be realized."
<end excerpt>
Michael