TEN years ago yesterday, George W. Bush warned Saddam Hussein that he had 48 hours to step down from power and leave Iraq, along with his sons, or face a US invasion. It's all gone a little hazy now; why exactly did this seem so urgent at the time, again?

The danger is clear: using chemical, biological or, one day, nuclear weapons, obtained with the help of Iraq, the terrorists could fulfill their stated ambitions and kill thousands or hundreds of thousands of innocent people in our country, or any other. ...Terrorists and terror states do not reveal these threats with fair notice, in formal declarations—and responding to such enemies only after they have struck first is not self-defense, it is suicide. The security of the world requires disarming Saddam Hussein now.

This, obviously, was all a fever dream. There were no biological or nuclear weapons; there may have been a few rusty chemical shells lying around, just as there had been for decades. Iraq was not an important sponsor of Islamicist terrorism. Islamicist terrorism was fueled not by fascist dictatorships such as Iraq, but by non-state actors in failed states such as Afghanistan and Somalia; and our invasion of Iraq promptly turned it into precisely the sort of failed-state sectarian war zone that does fuel terrorism. Thousands of American soldiers died in a war in Iraq that only exacerbated the danger of anti-American terrorism. Thousands of Iraqi soldiers died as well, and hundreds of thousands of Iraqi civilians died in the resulting civil war, most killed by the Iraqi militias who emerged in the power vacuum the US invasion created, but many killed by US armed forces themselves. In the name of pre-empting a non-existent threat, America killed tens of thousands of people and turned Iraq into a breeding ground for terrorism. And we spent a trillion dollars to do it.

How did America's policymaking community ever commit itself to such a catastrophic delusion? I don't truly understand it now, and I didn't understand it then. I found the developing consensus for an unprovoked attack on Iraq in late 2002 absurd. But I had an advantage: I wasn't living in America at the time. Viewed from the defamiliarising distance of West Africa, the American polity's effort to talk itself into invading a country that hadn't attacked it was baffling and disturbing. That reaction was widely shared in the country where I was living among locals and expats, Americans included.

Inside America, the atmosphere was entirely different, as I found after returning from Africa in early 2003. Large numbers of otherwise intelligent people had ended up supporting the war. Why? I think it had something to do with the iterative process of these sorts of discussions. You start out asking how to make sure Iraq doesn't have biological weapons, then you're asking how to respond to Iraq's refusal to comply with UN inspections, and before long through a series of individually rational steps you've arrived at a position that turns out to be a mistake. But the malign influence of intellectual conformity, the fear of being branded anti-patriotic or a foolish apologist for dictators, the nervous self-hatred of an intellectual class cowed into submission by an anti-intellectual president's popularity also all played a role. I remember spending a week in the offices of the New York Times's Outlook section in January; the anxiety to self-police against anything that could be perceived as liberal bias was palpable. Smart, serious people convinced themselves to accept the most spurious claims.

What I took away from it all was the depressing conviction that all of us, including those of us considered the most responsible, well-trained and serious, are entirely capable of talking ourselves into lurid fantasies; that the actions we believe constitute difficult but necessary choices may in fact be the gestures of sleepwalkers battling phantoms. This is a lesson we learn and forget over and over again. Two days after Mr Bush's warning speech, I headed off to a new foreign posting, and watched the tanks roll into Iraq on a TV in the passenger lounge of a South-East Asian airport; a few hours after that, I was arriving in Vietnam. So was the rest of America, but it didn't know it yet.

(Photo credit: AFP)