FIFTEEN months before the 9/11 attacks, the bipartisan National Commission on Terrorism, on which I served as chairman, reported to the president and the American people that we faced a new and terrible threat: the nexus between states that supported terrorism and killers who wanted to murder Americans by the thousands and were prepared to die doing it.

For decades, American administrations from both parties had designated Saddam Hussein’s Iraq a terrorist state. He supported and lauded Palestinian terrorists. He had developed, and used, weapons of mass destruction against his own citizens. He had contemptuously refused to comply with 17 Security Council resolutions demanding he come clean on those programs.

Our soldiers were magnificent in liberating Iraq. But after arriving in the country, I saw that the American government was not adequately prepared to deal with the growing security threats. Looting raged unchecked in major cities. By late 2003, as the insurgency and terrorism grew, it became clear that the coalition also lacked an effective counterinsurgency strategy.

Our troops on the ground were valiant and selfless, but prewar planning provided for fewer than half the number of troops that independent studies suggested would be needed in Iraq. And we did not have a plan to provide the most basic function of any government — security for the population. Terrorists, insurgents, criminals and the Iraqi people got the impression that the coalition would not, or could not, protect civilians.

I should have pushed sooner for a more effective military strategy, because from 2004 to the end of 2007, Al Qaeda took advantage of this gap, using indiscriminate killings that provoked Shiite militias to respond in kind. The vicious spiral was finally reversed by the change in strategy the president put in place a year ago.