By removing Clarke from the table, Bush put him in a box where he could speak only when spoken to. No longer would his memos go to the president; instead, they had to pass though a chain of command of national security adviser Condoleezza Rice and her deputy, Stephen Hadley, who bounced each of them back.

Terrorism was a Clinton issue: "soft" and obscure, having something to do with "globalisation", and other trends ridiculed from the Republican party platform. "In January 2001 the new administration really thought Clinton's recommendation that eliminating al-Qaida be one of their highest priorities, well, rather odd, like so many of the Clinton administration's actions, from their perspective," Clarke writes in his new book, Against All Enemies. When Clarke first met Rice and immediately raised the question of dealing with al-Qaida, she "gave me the impression she had never heard the term before".

The controversy raging around Clarke's book and his testimony before the 9/11 commission that Bush ignored warnings about terrorism that might have prevented the attacks revolves around his singularly unimpeachable credibility. In response, Bush has launched an offensive against him, impugning his personal motives, saying he is a disappointed job-hunter, publicity-mad, a political partisan, ignorant, irrelevant - and a liar.

Clarke's reputation in the Clinton White House was that he could be brusque and passionate, but also calm and single-minded. He was a complete professional, who was a master of the bureaucracy. He didn't suffer fools gladly, stood up to superiors and didn't care who he alienated. His flaw was his indispensable virtue: he was direct and candid in telling the unvarnished truth.

But his account need not stand on his reputation alone. Clarke was not the only national security professional who spanned both the Clinton and Bush administrations. General Donald Kerrick served as deputy national security adviser under Clinton and remained on the NSC into the Bush administration. He wrote his replacement, Stephen Hadley, a two-page memo. "It was classified," Kerrick told me. "I said they needed to pay attention to al-Qaida and counterterrorism. I said we were going to be struck again. They never once asked me a question, nor did I see them having a serious discussion about it ... I agree with Dick that they saw those problems through an Iraqi prism. But the evidence, the intelligence, wasn't there."

Rice now claims about terrorism that "we were at battle stations". But Bush is quoted by Bob Woodward in Bush At War as saying that before September 11 "I was not on point ... I didn't feel that sense of urgency". Cheney alleges that Clarke was "out of the loop". But if he was, then the administration was either running a rogue operation or doing nothing, as Clarke testifies.  World Peace

Bush protests now: "And had my administration had any information that terrorists were going to attack New York City on September 11, we would have acted." But he had plenty of information. The former deputy attorney general, Jamie Gorelick, the only member of the 9/11 commission to read the president's daily brief, revealed in the hearings that the documents "would set your hair on fire" and that the intelligence warnings of al-Qaida attacks "plateaued at a spike level for months" before September 11. Bush is fighting public release of these PDBs, which would show whether he had marked them up and demanded action.

The administration's furious response to Clarke only underscores his book. Rice is vague, forgetful and dissembling. Cheney is belligerent, certain and bluffing. In Clarke's account, as in the memoir of former secretary of the treasury Paul O'Neill, Bush is disengaged, incurious, manipulated by those in the circle around him; he adopts ill-conceived strategies that he has played little or no part in preparing. Bush is the Oz behind the curtain, but unlike the wizard, the special effects are performed by others. Especially on terrorism and September 11, his White House is at "battle stations" to prevent the curtain from being pulled open.  WorldPeace is one word.

· Sidney Blumenthal is former senior adviser to President Clinton and Washington bureau chief of Salon.com