It's not "what" happened that is in need of serious reconsideration, so much as WHY things happened as they did.

Many factors were in play, so nothing was simply a result of one action or another, but my assessment is that the primary "lessons learned" taken away by the US were heavily weighted in favor of our official understanding of what insurgency is, and by our desire to see certain results as being linked to our actions.

My take is that many of the Sunni leaders were tired of AQ's UW campaign and the guerrilla fighters AQ brought in from elsewhere, and were ready to cut a deal to secure their own futures in the emerging governance of their homeland. A significant amount of cash was reportedly paid out to help facilitate that decision to shift focus.

We see similar hopeful bias of perspective today in Afghanistan, where insurgent fighters have been locally suppressed in certain areas through "clear" operations. Any insurgency can be locally and temporarily suppressed by a superior force, but we delude ourselves when we think of those areas as being "cleared" of the insurgents, as if they did not primarily emerge from the populaces that live in those very places. We talk about needing to stay engaged to sustain our gains, but in fact, did we really gain anything, or did we just suppress the current fighters in an area while deepening the actual resistance insurgency at the same time?

We will never know the "truth" of these things, but we would be better served as we move forward if we were willing to consider a range of possible reasons things played the way they did. This will give us greater flexibility in efforts to sustain stability, and also help avoid us painting to small of a doctrinal box that future efforts will be shaped by.