In 1978, Israeli forces illegally invaded the southern part of Lebanon, and in 1985 declared that part of the country a security zone for its border. In 1982, Israel continued with its invasion up to and including Beirut. The United States, France, Italy and the United Kingdom sent a multi-national force to provide security while Israel pulled back and Palestinian forces left for Tunis.

The multi-national force left Lebanon in 1984. Under heavy fire from the newly found Lebanese Resistance, Israel partially withdrew from central Lebanon in 1984 and 1985 but enlarged its occupation of the southern part of the country up to the area of Jezzine.

Continue the history here 

Additional info here