The fact that we should never have entered Iraq is made clear by enumerating the mistakes made in calculations before declaring war.  This information is often used to incite further resentment against the war, but it’s too late for that.  Instead, we should use it to reflect upon the ways in which we might be deceived by too-easy plans to leave, or stay inside, Iraq–and aim to improve our approach. 

Before going in:
1. The U.S. did not exhaust all recourse through theinternational community before entering the war, must glaringly the International Atomic Energy Agency;
2. The U.S. Administration either misled or caused to lie, many previously respected officials in its cadre, including Secretary Colin Powell;
3. It damaged or ended the careers of many security personnel, including but not limited to that of Valerie Plame, through what Seymour Hersh has called “stovepiping” information without analysis and quashing dissent;
4. It dismissed generals who dissented about the means, methods, and strategies of this war, such as General Shinseki. 

There is a kind of gallows-humor joke that the war strategy was first waged in the White House with an animated Power Point presentation, and that ‘the suits’ thought it would be as easy as the animated arrows on the slides.

5. The planning for Iraq’s reconstruction, called “The Future of Iraq Project”, completed somewhat by the U.S. State department and consulting many respected experts such as Anthony Cordesman, was completely ignored–possibly because many of these experts were skeptical that a good outcome could be achieved.

In general, one could say that entry into the war was carried out through a wilful self-deception that cost many their careers and failed to use the knowledge capital available, within the United States and without.  For the U.S. to redress this grave, fatal error, it requires that we look not only with anger at the waste committed, but with an educated focus that comprises an understanding of military, social, and political study.  Though mostly fought with U.S. troops and at U.S. instigation, this was needs to be viewed through an international lens as well as a domestic lens.  That alone would make further policies a great deal more informed than our entrance was.

Further reading:
Against all enemies by Richard Clarke: just the last chapter is recommended, where it discusses the fruitlessness of Iraq’s engagement in terms of national security against terrorist threats.
Drinking the Kool-Aid by Colonel W. Patrick Lang, 2004
The Stovepipe by Seymour Hersh, 2003
Future of Iraq Project, 2001–all thirteen volumes.
The “Reach of War” page at the New York Times for the most current information.