The war in Iraq has become so divisive, and reactions to it so hardened and extreme, that I wonder how much interest there is in a detailed, dispassionate examination of the facts. For anyone with such an interest, though, Cobra II: the Inside Story of the Invasion of Iraq (2006), by Michael R. Gordon and General Bernard E. Trainor, is indispensible reading.
The book covers the run up to the war, the military campaign to overthrow Saddam Hussein's Baathist regime, and the military and political events following the fall of Saddam.
Despite the lack of discovery of weapons of mass destruction, the rationale for the war was not clearly wrong, and Saddam's own actions contributed to the conflict. Saddam played a dangerous game of attempting to deter foreign enemies (especially Iran) and internal enemies through a policy of creating uncertainty as to whether he had WMDs. This policy ultimately made it very difficult to say whether Saddam had the weapons or not. On the other hand, the Bush administration was so intent on regime change, that it is questionable whether a verified lack of WMD would have made any difference. And the removal of Saddam was, in itself, not a bad thing.
Unfortunately, the planning for the war and for the post-Saddam situation was very seriously flawed. It has become almost a cliche to blame these problems on Secretary of Defense Donald Rumsfeld. Cobra II amply documents that this cliche is, actually, quite correct. While Rumsfeld was not alone in making serious misjudgments (L. Paul Bremer contributed his share), Rumsfeld's leadership was simply disastrous. Rumsfeld's view of military modernization emphasized technology, speed, and mobility rather than numbers of troops. This led to planning based on using the least number of troops to get the job (the overthrow of Saddam) done. Further, Rumsfeld incorrectly believed that fewer, rather than more, troops would be needed in Iraq following the fall of Saddam. These mistakes, combined with thoroughly wretched intelligence from the CIA (which had previously performed well in Afghanistan), were a recipe for disaster.
Whatever the ultimate outcome in Iraq, the current situation was not inevitable. The world's misfortune, and especially the misfortune of the Iraqi people, arose because of the ignorance regarding Iraq and the ideological blinders of Secretary Rumsfeld and a few others.
This is an important book. If you don't have the time or inclination to work your way through all 500 pages, at least read the 10-page epilogue.