The problem with all this talk about mission goals is that there is ONLY ONE GOAL THAT MATTERS: getting our troops out of Iraq and leaving behind a self-governing, stable, West-friendly democracy.
Now, I and other sane people know that the chances of this happening are similar to a snowball surviving in Hades. I think the best we can hope for at this point is to allow Iraq to be divided into 3 countries.
Sunniville aka Sadamistan in the West
Kurdistan aka "Turkey's worst nightmare" in the North
and "New Iran" or "Little Iran" or "West Iran" in the East
After all, this is what they really want. It's high time we abandon our expectations for a new Iraq to become a shining beacon of democracy, tidy up the best we can and get the hell out.