What is President Barack Obama's objective in Afghanistan?

President Obama suddenly appoints Lieutenant General Stanley McChrystal, a man with a brutally bloody reputation in Iraq, rudely brushing aside General David D. McKiernan.

Is President Obama unleashing that rabid dog of war McChrystal upon the hapless Taliban in the hopes of... what?

A gore ridden success?

Or, perhaps, a gore ridden failure that will 'force' America to withdraw from oil-deprived Afghanistan without needing to 'win' a war, much like the 'truce' in Vietnam.