Read this, about negotiations with the Iraqi government about the terms for our troops being there. We dethroned Saddam Hussein and set up a freely-elected government. That mission actually was accomplished. The way out of Iraq is to leave when that government requests us to. When the government is so unstable that it needs our troops to keep its members alive, it will want us to stay. When it attains a level of stability, which it may have reached, to the point that occupying troops are a political liability, it will request us to leave, which will be our way to do so without surrender. (I actually made this case at the outset of our invasion, and it looks like, as sometimes happens, I may have been right, as far as how things are unfolding.)