One of AS's reader's writes:
The ugly truth is, the only way there's going to be a settled peace in Iraq is if the two (at least two) sides fight it out, and separate their populations. If we were to stay there with current troop strength for 30 years, this would still be the case.
AS has suggested, as have others, that a 're-configuration' (a better term than re-deployment) of forces to Kurdistan might be an option (even though many Kurdish leaders are wary of such a move).
Consider another move, perhaps more sophisticated.
A WAY TO USE PLANNING TO SHAPE AND FORCE COOPERATION IN THE PRESENT
Leak military and diplomatic plans to redeploy along the Iranian border, with extensive plans for electronically sealing the border. Start some false construction projects to support the logistics for such a move, so it is not clear whether such plans are a bluff or not.
It stands to reason that such prospects will knock the wind out of the sails of those who think that they are going to open up supply lines to Iran, during a civil war.
No good ideas - yet - on how to similarly manipulate the calculations of the Sunni hardliners, but it doesn't seem impossible.