Like Brian Beutler, I've long been fascinated by the war the Iraq War appears to have spawned a whole new category of organized violence -- whatever it is that's happening in Iraq that somehow isn't a "full-scale" civil war. Call it the half-scale civil war. It sounds like BS to me.
No, Iraq's civil war doesn't look like the American Civil War, but if that's what we mean by "full-scale civil war" then it's almost certainly not the case that "the surge is keeping Iraq from descending into" one. That the groups who deny the legitimacy of the de jure government and the US occupation authority and deploy violence or the threat of violence in service of their political goals don't necessarily wear uniforms and fight in formation is rather typical of these kind of situations and not something the surge is preventing. Looked at a different way, Iraq's civil war is notable for the fact that the contending parties' don't have much in the way of heavy military equipment. That's all to the good, and we have good reasons for continuing to support efforts to keep things that way post-withdrawal, but efforts in that regard don't require the presence of over 150,000 American soldiers on the ground.
Public domain photo of the Gettysburg dead by Alexander Gardner