Austin Long has an interesting paper out at RAND on the history of COIN doctrine in the U.S. military. Here’s how he sees the situation in Iraq (it’s a long quote but worth reading):
After a near-disastrous 2006 that saw rising violence in most of Iraq, 2007 saw improvement in the security environment, most strikingly in al-Anbar province but also in Baghdad. Some credit changes in military practice related to the new COIN doctrine with this improvement, along with an increase in troop numbers. While a detailed assessment of the situation is beyond the scope of this paper, it is important to note that the central improvements in security have resulted from fractures between insurgent groups rather than a major change in U.S. operations.
As late as November 2006, Marine intelligence painted a grim picture of al-Anbar despite the doctrinally sound efforts in places like Al Qaim and Ramadi. However, many tribes were in the process of splitting from Al-Qaeda in Iraq (AQI) and realigning with the United States (and to a lesser extent the central government of Iraq). While the United States proved flexible in exploiting some of these fractures, U.S. successes occurred independently of doctrinal change. Furthermore, these maneuvers have not resulted in conditions amenable to long-term stability under a unified government. Instead, various tribes and factions jockey for power even as AQI lurks in the hinterland. Elsewhere, success is mixed or absent. In and around Baqubah, north of Baghdad, AQI and Shia militias such as Jaysh al-Mahdi battle to dominate the population.
Some operational shifts have taken place. Many smaller bases have been opened, particularly in al-Anbar and in Baghdad. Partnering with Iraqi security appears to be taken much more seriously. Yet wide variation in U.S. military unit attitudes toward Iraqis (both in uniform and out) persists, and disagreements about COIN are still obvious at senior levels. Sometimes these disagreements have serious consequences in terms of operations undertaken or foregone.