The question, once we decide to leave Iraq is how do we sterilize it? (In the medical sense, not the reproductive sense.) Think about it. It's in our national interest to prevent the spread of jihadis and to prevent a regional war (doing both may well be impossible). So, how do we do it? Bargain with Tehran? Muscle Syria? Let the Saudis spread oil money around the Sunni parts of Iraq? There are a hundred more moving parts to this. It's east to see what the politicians in Washington are in denial--the consequences of Bush's folly are truly grim in a way the consequences of Vietnam were not.
More on this later.