Based on my personal experiences and first hand knowledge of events during the buildup and first year of the war in Iraq I sincerely believe that Donald Rumsfeld was responsible for the problems that developed during that first year: problems that are affecting us to this day.
Persons other than Don Rumsfeld made critical mistakes but he took control of the planning for and execution of the invasion and deliberately excluded the Department of State and other agencies from any significant participation in the planning for or execution of the occupation. I can't say that greater DOS participation in the occupation would have improved the results but they could hardly have made them worse. The occupation was begun with minimal planning or preparation. As a result the military forces in Iraq were left to occupy the country with little guidance from the political authorities that had ordered the invasion.
As an Army colonel working to assist the Marine forces in the occupation of the southern half of Iraq, I had direct access to the planning documents and had personal knowledge of their inadequacy. I watched as the Marine commanders tried to govern a large, populous Arab country through trial and error and improvisation. They did the best they could under the circumstances. We all did.
When I left Iraq I was convinced that Rumsfeld was to blame for the fundamental problems that we faced and have continued to face. From all acounts, Rumsfeld is a brillant, extremely hard working, experienced and capable administrator. He believed (and still believes, for all I know) that he did the right thing. I believe that he should have been removed years ago, and for that I hold the President responsible.
Now that Mr. Rumsfeld has been removed from the post of the Secretary of Defense I hope that he will write a book that explains to us all why he took the actions and decisions that he did. In particular, I want to know why he didn't apply that brillant and capable mind to ensuring that there was an adequate plan for the occupation. My great fear is that his book, if it even comes, won't adequately address that question.