Headhunter is correct on the timeline for withdrawal, physically it will take a while. Normal civilians don't realize the logistics of getting all our troops and equipment out of Iraq.
You just can't tell 150,000 soldiers and marines to report to the airfield to get in line to go home. Were not going to be like the russians and leave all our tanks, planes, bombs, behind like they did in Afghanistan and somalia.
Im gonna throw out an estimate and say if Obama says we pull out tomorrow, all soldiers won't be home for 18-24 months.
...and while this is taking place don't think for a second the insurgents are going to sit and nicely wave goodbye. There going to do whatever they can to grab control and power and kill anyone who ever helped the coalition forces.