The United States is headed into the sixth year of an exceptionally frustrating war whose consequences so far have been largely injurious to America's long-term national security. Preoccupation with that war understandably has obscured the original decision for launching it. That decision cannot be repealed, and the controversies surrounding it offer little guidance to those grappling with the political and military challenges confronting the United States in Iraq today. Knowing the way into Iraq is not knowing the way out. That said, it is critical that Americans come to understand how the United States came to invade and occupy Iraq, if for no other reason than to inform future discussion of whether, when, and how to employ US military power. Understanding how we got into Iraq may help us avoid future "Iraqs."