Not too long ago, Dick "In Denial" Cheney pointed to Basra, Iraq as a place "where things are going pretty well."
British troops are in the process of pulling out of Basra, which is an almost entirely Sh'ite city. As they do so, Shi'ite militias are battling each other for power. As today's Washington Post reports, "[t]hree major Shiite political groups are locked in a bloody conflict that has left the city in the hands of militias and criminal gangs, whose control extends to municipal offices and neighborhood streets. The city is plagued by 'the systematic misuse fof official institutions, political assassinations, tribal vendettas, neighborhood vigilantism and enforcement of social mores, together with the rise of criminal mafias.'" ("As British Leave, Basra Deteriorates")
We can expect the same--but worse (throw in Sunnis) when the U.S. leaves Baghdad, whether that's in a few months, or a few years.
Here's some food for thought for history buffs: after four years of Civil War in the U.S., northern troops occupied the South for another 12 years, until 1877. After the disputed Presidential election of 1876, a "compromise" was reached under which the last remaining federal troops were withdrawn. Immediately thereafter, whites enacted Jim Crow laws that remained in effect for nearly another century.
We can stay in Iraq as long as we want. When we go, scores will be settled.