If they don't want to leave, all Israel has to do is pull the military out and let the settlers defend themselves.
I never understood it either. The Israeli government is heavily subsidizing those people to live there and is paying them to leave.My suspicion for awhile has been that the Israeli government would rather have them playing pioneer in the West Bank than pestering less-than-observant Jews in Israel proper. A combination of US pressure, the cost, and increasing military dislike for service in the territories (service in Hebron is particularly unpopular for non-orthodox troops) is causing this philosophy to be reconsidered.If they don't want to leave, all Israel has to do is pull the military out and let the settlers defend themselves.
There's little if any chance of Israel retreating to the "Green Line". Unfortunately, the settlements that are the most isolated and the least defendable (Gaza, Hebron, and Itamar come to mind) also contain the settlers that are there for ideological rather than financial reasons, and will resist the hardest.
Sharon's walking a tightrope, and he's in the middle, the toughest part.
-Eric