Judah Grunstein concedes a few points about the surge:
...the Surge did accomplish two things. By signalling Bush's unwavering commitment to America's military engagement, it helped convince the various Iraqi factions that whether or not they ultimately resolve their differences through bloodshed, they'd stand to gain by waiting until after we're gone to do so. And should the security gains hold until the American drawdown is complete (whenever that is), the Surge will have allowed the American military to withdraw from Iraq with its coercive reputation intact. And that's indispensable if American power, in both its soft and hard expressions, is to be credible.
If you see the surge as an exit strategy, it makes some sense. As Petraeus himself notes, he was also lucky - and shrewd enough to capitalize on his luck. The question that still worries me is whether the Awakening Movement can come to terms with the Shiite government. I see plenty of reasons for extreme worry on that count. I think some civil war is inevitable once we leave, if we ever do.