There is a reason the generals are not in charge of our country – by design, anyway. The Gateses and McCrystals of the world are the real barbarians, personally and professionally locked on a treadmill that demands ever more blood and more glory, at any cost. With the publicly accepted mission in Afghanistan accomplished, Americans cannot afford to entertain the vain fantasies of flag officers who fear nothing but their own oblivion, and will sacrifice any number of lives and all measures of treasure in pursuit of personal relevance.
While "Al Qaeda" is a fantasy concocted by the American government, and Osama bin Laden is dead, getting the heck out of Afghanistan right now is one of the most intelligent things the US could do right now.
Unfortunately, intelligent decisions and US government have rarely had an on-going relationship.