CSIS just published a report looking at the same topic from a different perspective: The Iraq War and Its Lessons for Developing Local Forces
Iraq, like so many other serious Post-WWII insurgencies, shows that successful counterinsurgency means having or creating a local partner that can take over from US forces and that can govern. Both Vietnam and Iraq show the US cannot win an important counterinsurgency campaign alone. The US will always be dependent on the people in the host country, and usually on local and regional allies. And to some extent, will be dependent on the quality of its operations in the UN, in dealing with traditional allies and in diplomacy. If the US can’t figure out a way to have or create such an ally, and fight under these conditions, a counterinsurgency conflict may well not be worth fighting.

This means the US must do far more than creating effective allied forces. In most cases, it find a ways to help its partners reshape their process of politics and governance so that the development of security forces is matched by the steady development of governance, and a matching civil presence and the provision of effective government services.