After four painful years, the US military has stumbled upon (mostly due to the now classic Jihadi overreach -- as in Afghanistan, Somalia, etc.) the only model for fighting a mature open source insurgency: a decentralized model of security that forgoes centralized defense/police forces in favor of a plethora of independent militias. The success of this model in reducing violence (at least in the short term) in Anbar province, has led to its replication in other provinces.
This effort is essentially open source warfare in reverse (another way of looking at it is as the counter-insurgency equivalent of IBM's embrace of open source software -- a path I pointed out in the NYTimes back in 2005). In this model, the US military aligns itself with a plethora of militias (in this case hundreds) regardless of political/regilious/ethnic/tribal affiliation under the plausible promise of local autonomy. It is made fact as funds, weapons, and local control flows to these militias.
How this plays out over the next couple of years will be interesting to watch. It's fairly obvious that the US military doesn't have the skill sets for successfully managing this level of complexity (here's a minor example: it doesn't even have a relationship management system for tracking interactions with these militias -- something that could easily be constructed through a redux of commercial CRM software). It also runs counter to all of the classic goals of counter-insurgency and more importantly, the stated (and implied) goals for the US in Iraq:- A viable central government. Every time a militia is stood up, it is at the direct expense of the central government. It loses the essential requirement for any viable state: a monopoly of force.
- A grand political bargain. An open-source counter-insurgency locks Iraq into a patchwork of mini-fuedal principalities with a large diversity of primary loyalties. Political settlement now becomes impossible since the sheer diversity of armed interests will overwhelm any attempt at reconciliation.
- A safe place for private oil companies and a long term US military presence. This new patchwork of armed groups in Iraq ensures chaos, which will make it impossible to attain any level of modern normalcy. Vendettas between militias, betrayal (of US troops), rampant crime/theft/corruption, and more is on the dinner plate for decades to come. Finally, the open source insurgency won't go away. It will only return when it revises its methods in light of the new conditions.