From Barry McCaffrey:
We could immediately and totally withdraw. In less than six months, our 150,000 troops could fight their way along strategic withdrawal corridors back to the sea and the safety provided by the Navy. Several million terrified refugees would follow, the route of our columns marked by the burning pyres of abandoned military supplies demolished by our rear guard. The resulting civil warfare would probably turn Iraq into a humanitarian disaster and might well draw in the Iranians and Syrians. It would also deeply threaten the safety and stability of our allies in neighboring countries.