Folks know that I like counterfactuals, so I thought I might muse on a point that I think's gotten too little attention. Thus far, discussion of tactics in Iraq has tended to focus on either the question of whether things could have gone better had we gone in with a larger force and better counterinsurgency tactics in 2003, or else on how big of a positive impact the "surge" had over the course of 2007. Another point worth considering, however, is whether smarter policy back in 2005 couldn't have avoided the mass bloodshed of 2006 and early 2007.
After all, January 2005 would have been a very logical time to start packing up our bags and going home. After deposing Saddam and putting a new governmental framework in place, the United States came to be faced with an anti-American insurgency. We were having little success in actually beating the insurgents, but the violence in Iraq wasn't causing the huge levels of destruction that we would see later. What's more, at that point in time it wasn't considered acceptable for mainstream figures to muse about staying in Iraq for 100 years or to editorialize that keeping troops in Iraq is more important than defeating al-Qaeda in Central Asia because Iraq "contains some of the world's largest oil reserves".
Instead, the reason given for why we had to stay in Iraq was that if we left Iraq there would be civil war, sectarian violence, and ethnic cleansing. Since we know all of that happened anyway it seems reasonable to second guess the decision-making that led us to stay. What would have happened if sometime in November or December of 2004 the Bush administration announced that while it wasn't prepared to schedule a departure from Iraq, it was looking forward to negotiating a timetable for withdrawal with the new Iraqi government to be elected in January? Well, it seems to me that a few things would have happened. One is that Sunni Arabs would have participated in the elections at a higher rate. Another is that insurgent groups would have had much less reason to make common cause with AQI. And a third is that Muqtada al-Sadr would have been deprived of us best "wedge issue" to use against the other Shiite parties.
We would have bequeathed to Iraq, I think, something that looks a lot like Iraq today -- a chaotic situation where the government has little capacity and where things could fall apart in various ways, but where there isn't the kind of ongoing boiling-over civil war that in fact came to haunt the country.