The 1982 Lebanon War, also called the Second Israeli invasion of Lebanon, began on 6 June 1982, when Israel invaded southern Lebanon. The invasion followed a series of attacks and counter-attacks between the Palestine Liberation Organization (PLO) operating in southern Lebanon and the Israel Defense Forces (IDF), which had caused civilian casualties on both sides of the border. The Israeli military operation, codenamed Operation Peace for Galilee, was launched after gunmen from the Abu Nidal Organization attempted to assassinate Shlomo Argov, Israel's ambassador to the United Kingdom. Israeli prime minister Menachem Begin blamed the PLO, using the incident as a casus belli. It was the second invasion of Lebanon by Israel, following the 1978 South Lebanon conflict.