After reading many articles supporting either a surge in American presence or an almost unconditional pull-out of Iraq, this is my simplification of the issue:
By invading and defeating the Iraqi government, we assumed a degree of responsibility for the safety of her people, meaning that we can't just abandon them to civil war.
While all three major ethnic/religious groups profess they want to retain Iraq a unified country, the intensity of their fighting one another in no way reflects this so loudly professed wish.
We might have to face the necessity of having to leave Iraq divided into three parts unless her religious and secular leaders and their followers act in such a way as to convince themselves and the world that they have the will, the love and the maturity to live and work together humanely and peacefully.
We should leave Iraq based on the actions of the Iraqi people over the next few months: either united or divided in three. It would be presumptuous for us to try to take such a momentous decision out of their hands.