The Mountanous and Valley regions of Lebanon are much more rugged than Jenin's landscape.The Lebanese can hide in caves, either man made or natural, and wait until they want to attack. There is no way to bomb a mountanous region into submission from planes, simply no way.Also, a well motivated domestic mountanous force is very hard to remove from the ground.They just have too many places to hide and the terain is too rough for easy passage of tanks, buldozers and the like. Those equipments require much flatter terain to be most effective. There is simply no place harder to fight than in a mountanous region, and although the mountains in Southern Lebanon are pretty small and unempressive, they are rugged enough to screw up an invading force. Remember also that in the first Lebanon war, Israel faced PLO/mercinary soldiers using Soviet tanks etc, and not indigenous force. Many if not most ran in the face of the invading Israeli army.(I had buddies who reported simply hopping in the tanks.
Israeli moderately wounded in stabbing attack near West Bank settlement (Haaretz)
from the article: Wounded troops describe Bint Jbail battle as 'hell on earth'