Joe Klein:

There is one argument for continuing the fight that I would add, however:

Pakistan. If the U.S. doesn't remain engaged in Afghanistan, the civilian government in Pakistan - already an incredibly shaky enterprise - will probably fall.

Our presence in the region is one of the main destabilizing factors. Pakistan and India were having productive talks before we set down a large military presence in the area. Now their people are angry and the fundamentalist forces are on the rise. Here's why.