In response, on 14 March 1978, Israel launched Operation Litani occupying southern Lebanon, except for the city of Tyre, with 25,000 troops. The objective was to push the PLO away from the border and bolster a Lebanese Christian militia allied with Israel, the South Lebanese Army (SLA). However, the PLO concluded from the name of the operation that the invasion would halt at the Litani River and moved their forces north, leaving behind a token force of a few hundred men. As a result, the casualties were almost all civilians.