One possibility, of many, is that when the US leaves Iraq, Iran will step in and annex Iraq either formally or de facto. Iran and Iraq have already fought a bitter war in which Iraq used chemical weapons and we, under Reagan’s guidance, sided with Saddam Hussein. If Iraq descends into chaos after we leave, can we expect Iran to keep hands off? If the Shiites are unquestionably in power when we leave, Iran might stay out. On the other hand, if there is the least chance of the Sunnis taking over again, why should Iran risk it. It would be foolish for Iran to take that risk. The US intervened strongly in Central America during Reagan’s presidency when we thought the Communists were coming to power there. There is likely to be an Iranian Ollie North who will push for invasion, maybe using some weapons supplied by the real Ollie North.
Should that possibility keep us from leaving? Maybe, but only if staying could change that outcome. If staying just keeps the lid on anarchy until we finally leave, what’s the point? Iran could take over in 2008 or 2010 or 2020; it still takes over. We could hope for some kind of revolution in Iran, but it’s unlikely to happen.
I think that we need to beef up the troops and re-establish order in Iraq, but Bush and the Republicans are too cowardly to do it. They won’t re-establish the draft, which would be the only way to raise a sufficient number of troops to do the job. They’ll just keep sending the same troops over there again and again for longer and longer tours with shorter and shorter stateside tours.