[There was a] rift between strategy and tactics: winning the battle but losing the war; fighting the insurgency, not the insurgents; the people are the prize, not the enemy - a classic counterinsurgency point.
[U.S. Leaders mistook] the American public as the center of gravity, thereby painting a rosy picture of the declining predicament - when the real focus should have been the Iraqis, to win their 'hearts and minds'.
The inevitable and necessary rotation of troops that would expose newcomer troops to the steady cacophony of gunfire and explosions, while negating all the hard work in establishing rapport and personal connections that the previous troops on the ground had already accomplished. New negotiating partners, coupled with the hostile environment and paranoia as to whom one could trust, would lead to frequent misunderstandings and miscommunication.
These are only a few of the excellent points brought up in the post, so go ahead and read the whole thing. I am adding Fiasco to my reading list, although admittedly I have fallen behind on professional reading in recent days.