With the withdrawal of the 3rd Brigade, 1st Cavalry this month, the first of the "Surge" brigades has returned from Iraq. This marks the beginning of the end of the Surge. So far, has the Surge been a success?
To answer this question, I'm going to compare the cost incurred by the Surge compared to the benefits of it. I'll try to disaggregate the recent positive trends (emphasis on trends - the overall rates of violence, etc. are still horrific) in Iraq from the effects of the Surge itself.
Costs fall in three categories - money, lives, and opportunity. It's difficult to estimate the monetary costs of sending five extra brigades to Iraq (the Surge). The Pentagon throws all sorts of junk in with their "emergency" funding requests for Iraq and Afghanistan, meaning it'd be extremely tedious to go through the text of their requests to see how much is budgeted for operations pre-Surge and post-Surge. The White House's estimate was $5.6 billion, while the GAO estimated that the costs will be "up to $27 billion" for the Surge (CNN).
It's impossible to measure the cost in terms of U.S. lives. The Surge has put more U.S. personnel in Iraq as targets for insurgents and terrorists, and U.S. casualties were the highest in early 2007 (the beginning of the Surge) as they ever were. However more brigades means Coalition military power can be concentrated in problem areas like Diyala. For my purposes I'll call the "lives" cost a wash.
In terms of opportunity costs, sending our last five brigades to Iraq means that we have no brigades in reserve. If something unexpected happens in the rest of the world - for example if North Korea crosses the DMZ - we'll be able to send no reinforcements. Of course this only matters if something like that happens- fairly unlikely, but of course the whole point we have an expeditionary military capability in the first place. Our lack of reserves also means we're unable to send troops to troubled spots like Darfur that need resources only Western militaries can provide, although it's unlikely we'd send troops there anyway.
Over the course of the Surge, trends in Iraq have gone from entirely negative to mixed. According to DoD, violence against civilians is down to February 2006 levels (before the bombing of the Samarra mosque), while violence against Coalition targets is down to summer 2005 levels. These improvements are not entirely due to the Surge (and again I'll stress that the levels of violence are down to a time back when Iraq was widely considered to be in a civil war).
The decrease in violence is due to a number of converging factors. First of all, the Surge convinced many insurgent groups to lay low to wait out the temporary increase in American forces. When the additional U.S. forces leave, as they have already started doing, these insurgent groups may pick up their weapons again. Second, Jaysh al Mahdi (the militia loyal to Moqtada al Sadr) imposed a truce on itself after they massacred religious pilgrims in Karbala. Third, the U.S. forces' change in tactics from an enemy-centric strategy (i.e., where your focus is on killing bad guys) to a population-centric strategy (where your focus is on getting the local population on your side) would have resulted in lowering civilian deaths without a Surge (although may have raised American casualty levels in the short term). Fourth, ethnic cleansing operations in Baghdad and elsewhere have passed their peak as many neighborhoods are totally cleansed.
Finally and most important, the Anbar Awakening hit full force in Anbar province, coinciding with the Surge. The Awakening movement, now spreading across Iraq (but not without resistance from the central government), allowed the U.S. military to coopt the tribal forces that were allowing Al Qaeda in Iraq to target Americans in Anbar province. The U.S. thus eliminated an enemy and were able to assist local tribes eliminate an Al Qaeda safehaven in Anbar, lowering violence rates against both U.S. troops and civilians. I assume the Surge, giving extra units to Anbar, made the task of rolling up Al Qaeda cells in Anbar quicker, but that same effect likely could have been accomplished by transferring units from quieter parts of Iraq anyway.
Thus of the positive trends in Iraq, none of them have really been due to the Surge in American troop levels. In addition, the Surge has accomplished nothing politically in Baghdad - the Iraqi government in Baghdad remains as irrelevant as it ever has been. The Surge's original logic - to improve the security situation in Baghdad to give the central government the "breathing space" necessary to accomplish political reconciliation - has been a total failure, as the central government hasn't accomplished anything in months.
The Surge cost the U.S. billions of dollars and risked (and still risks) leaving the U.S. totally unprepared for contingencies around the world. In exchange we got little or nothing. While some insurgent groups may have decided to lay low during the period of increased American troops, that merely displaces current violence into the future, while those groups use the time to regroup, retrain and rearm.
Bush's Surge policy is/was a failure. Only the skill of a new leadership team in Iraq, the completion of Iraqi ethnic cleansing operations, and liberal amounts of luck have prevented the Surge's failure from being obvious. Instead, lazy journalists (and hacks) attribute the positive (and probably temporary) trends in Iraq to the Surge, giving Republicans (like McCain) political cover for failed policies. Credit, instead, should go to the mid-level officers who helped facilitate the tactical alliances with Sunni tribes in Al-Anbar, to people like Abu Risha and Abul Abed of Amariyah (a nutcase, but OUR nutcase), who took it upon themselves to fight Al Qaeda in Iraq, and to Lady Luck, the best ally of any military.