The Multinational Force in Lebanon (MNF) was an international peacekeeping force created in August 1982 following an 1981 U.S.-brokered ceasefire between the Palestine Liberation Organization (PLO) and Israel to end their involvement in the conflict between Lebanon's pro-government and pro-Syrian factions. The ceasefire held until June 3, 1982 when the Abu Nidal Organization attempted to assassinate Shlomo Argov, Israel's ambassador to London. Israel blamed the PLO and three days later invaded Lebanon. West Beirut was besieged for seven weeks before the PLO acceded to a new agreement for their withdrawal. The agreement provided for the deployment of a Multinational Force to assist the Lebanese Armed Forces in evacuating the PLO, Syrian forces and other foreign combatants involved in Lebanon's civil war.