I have always understood Bush's position, from the context of my having lived through the times, to be that we had to guard against use of Iraqi WMD on our soil through the agency of a terrorist group cooperating clantestinely with Iraq. Sirs is an ass.
Michael, as is often the case, makes some very trenchant comments. The question of timing is essential: WHEN would the feared attack be launched? One has to consider in this regard preparation time, which subsumes the very practical problems of how to transport the weapons, the need to train and install the agents, and then to plan and execute the attack. To a large extent, these activities already came under the watchful eye of CIA, FBI, state and local law enforcement, tangentially the Department of Defense, and squarely the nascent Department of Homeland Security. This array of defenses raises the damnable specter of a redundant war, if not one aimed at a spectral threat.
Further, and crucially important, on known intelligence the "remedy of war," especially as it's unfolded, is grossly disproportionate (causes human death and suffering exponentially greater than that "expected" for us) to the harm an attack WITHIN THE REALM OF RATIONAL PREDICTION could inflict on us.
The national debate at the time never progressed this far.