When you study how the U.S. goes to war, there is a prevalent though not perfect pattern. The triggering event is often a sudden crisis that galvanizes popular opinion and becomes the immediate occasion for military intervention but subsequently is exposed as a misguided perception or outright fabrication.

The Mexican War began when President Polk cited an attack on American troops in Texas — troops he had deliberately placed there to provoke Mexico. The Spanish American War began when President McKinley claimed that the battleship Maine had been blown up by Spanish saboteurs; subsequent investigations showed that the explosion originated inside the ship, probably due to an accidental fire in the munitions compartment.

More recently, the Vietnam War moved into high gear when President Lyndon B. Johnson used an incident in the Gulf of Tonkin to justify massive military intervention in Southeast Asia. The incident occurred in disputed waters, and one supposed gunboat attack never really happened. The enemy might very well have been a pod of whales.

This pattern is not perfect. The Japanese attack on Pearl Harbor was not a figment of President Franklin D. Roosevelt's imagination. Nor have subsequent conspiracy theories arguing that he was willfully negligent, searching for a "back door to war" against Germany, stood the test of time.

American military intervention in Iraq, however, fits the pattern perfectly. As we watch the enormous U.S. investment in blood and treasure over the last 11 years dissolve in Iraq, history requires that we remember the reasons we went to war, why they were untrue and why the current sectarian chaos in Iraq was always both predictable and inevitable...