After defeating the Taliban dictatorship in Afghanistan and replacing it with a fledgling democracy, the Bush administration turned its attention to the risk that Saddam Hussein’s Iraq was thought to pose to a nation still reeling from the attacks of 9/11.

I shared the administration’s belief that Iraq not only possessed the capacity to produce weapons of mass destruction, it also had a hidden stockpile of them. Responsible for two wars with more than a million dead, involved for decades with terrorist groups, routinely rewarding suicide bombers with cash, unwilling to document the disposition of chemical and biological weapons ( some of which he had actually used), Saddam Hussein forced the question: Should we leave him in place and hope for the best, or destroy his regime in a lightning strike and thereby end the risk that he might collaborate with terrorists to enable an attack even more devastating than 9/11?

The right decision was made, and Baghdad fell in 21 days with few casualties on either side. Twenty-five million Iraqis had been liberated and the menace of Saddam’s monstrous regime eliminated.

Then the trouble began. Rather than turn Iraq over to Iraqis to begin the daunting process of nation building, a group including Secretary of State Colin Powell; the national security adviser, Condoleezza Rice; and the director of central intelligence, George Tenet — with President Bush’s approval — reversed a plan to do that.

Instead, we blundered into an ill-conceived occupation that would facilitate a deadly insurgency from which we, and the Iraqis, are only now emerging. With misplaced confidence that we knew better than the Iraqis, we sent an American to govern Iraq. L. Paul Bremer underestimated the task, but did his best to make a foolish policy work. I had badly underestimated the administration’s capacity to mess things up.

I did not believe the American-led coalition could prudently leave Iraq the day Baghdad fell. Coalition troops were essential to support a new Iraqi government. But I was astonished (and dismayed) that we did not turn to well-established and broadly representative opponents of Saddam Hussein’s regime to assume the responsibilities of an interim government while preparing for elections. Our troops could have remained, under the terms of a transparently negotiated agreement, to help the people of Iraq build their own society, something we didn’t know how to do and should never have tried. After five years of terrible losses, they may now be getting that chance.

Richard Perle was an assistant secretary of defense in the Reagan administration. He is a fellow at the American Enterprise Institute.