What's The Exit Strategy?

Bing West, yesterday:

A year from now, coalition forces should be able to gradually withdraw, replaced by robust support and adviser units embedded in Afghan security forces. We shouldn’t make this a NATO war, allowing the Afghans to stand back. We’re outsiders, no matter how many schools we build or cups of tea we drink.

Drum:

Nothing West says here is especially controversial, really, except for that "a year from now" part.  But why shouldn't we begin withdrawing in 2010?  Al-Qaeda is essentially destroyed, seven years of occupation doesn't seem to have improved our ability to fight the Taliban, and bringing in the DEA isn't likely to help things.