I just watched the second part of two-part Frontline documentary called "Bush's War". The documentary manages to show the actual process of decision-making that led to such catastrophic policy disaster. Frontline is alone on TV in that it deeply examines the issues of the world today.
There are a lot of things one could learn from this. I suspect that many people will be surprised, for example, that Donald Rumsfeld advocated of withdrawal from Iraq since the very beginning. It also illuminates the mis-rule of Paul Bremer, the de facto US pro-counsel in Iraq. For those who do don't remember, Jay Garner was the original US man in Iraq, however, the administration lost faith in him. Bremer came in with a mandate to dismiss all Ba'athists. He formulated his own plan to dismiss the army. Both of these choices would have dire consequences.
The ultimate lesson is that many of the problems we face are of are own making. Dismissing the army created an angry, unemployed armed group. Our failures in Fallujah created our own Gaza, and then are attack led the Sunnis to boycott, creating an sectarian government without Sunni representation.
Both parts of the series (the first of which I have yet to watch) can be viewed here.
Of course, while the documentary illuminates many of the tactical blunders, we should not forget that the war was itself a strategic mistake. The idea was that this would be an easy victory, and in a strategic sense would scare rogue-states. Even from the beginning, it should have been obvious this result could not be achieved. The administration completely failed to understand that the number of troops needed to pacify this country would be greater than the military could muster (General Shinseki was dismissed by then administration after he estimated, based on standard military doctrine that, that the occupation would take hundred of thousands of troops). While the documentary misses the wider strategic failure, I still very much recommend it to anyone who wishes to have a deeper understanding of our failure on Iraq.