Unfortunately, Pakistan is the only friendly country with a seacoast bordering Afghanistan we can use to supply our troops there. Our garrison in Afghanistan is too big to be supplied by air, and the air routes go over very undependable (or downright hostile) states as well. If we want play in Afghanistan, we have no choice but to deal Pakistan in. And of course, as long as we're in that part of the world, Iran is surrounded.

There are other reasons, too. Afghanistan provides us with intelligence, and their troops do occasionally engage terrorists in their own country, even if not as often or as enthusiastically as we'd like. We also have bombing rights in their country, all those huffy complaints are just for domestic consumption. Also, Pakistan has nuclear weapons, and if the terrorists take over there, we are in big trouble.

OTOH, the Pakis need us too. They are terrified of a coup from their Islamists, they are paranoid about India, and their army will starve without our aid. Now that we have Bin Laden and have proof of Paki double-dealing, I suspect they will be more cooperative. We would lose if we left that part of the world, but they would lose everything.

Of course, if the President decides that leaving Afghanistan is in our interest now, then this would be the best time to do it. Even GOP hawks are getting fed up with the Pakis, and a dead Osama gives us a perfect, face-saving excuse. In fact, I think that is exactly what Obama is up to. He knows Afghanistan is the only way to get to the Taliban and Al-Quaeda, but if after ten years we can't show any better results than this, then maybe we're wasting our time there. I think the Republicans are being subtly manipulated into begging him to withdraw.