…Mr. Bush's own words on the subject have been a moving target. In the State of the Union address a week ago, he referred to "weapons of mass destruction-related program activities" that inspectors had found, drawing the wording from Dr. Kay's interim report last fall. He did not mention Dr. Kay's other conclusions: that those activities were largely in research and development, that most made little progress, and that they were intended to deceive Mr. Hussein into thinking that he was spending money fruitfully.

Scott McClellan, the White House spokesman, argued Tuesday that Mr. Bush had never said that Iraq posed an "imminent" threat, but only a "grave and growing" one. That may be literally correct, but both Mr. Bush and his aides made it clear many times that they believed Mr. Hussein already had unconventional weapons.

For example, on Oct. 7, 2002, during a speech in Cincinnati that laid out how America was threatened by Mr. Hussein, Mr. Bush said: "If we know Saddam Hussein has dangerous weapons today — and we do — does it make any sense for the world to wait to confront him as he grows even stronger and develops even more dangerous weapons?"

Secretary of Defense Donald H. Rumsfeld, speaking to the House Armed Services Committee on Sept. 18, 2002, said, "We do know that the Iraqi regime currently has chemical and biological weapons of mass destruction."

Such statements were important then because Mr. Bush had to convince the country and his allies that, especially in the post-Sept. 11 world, he could not wait to build a broader coalition against Mr. Hussein.

Moreover, international law has been far more forgiving of "pre-emptive war" against a country about to begin a strike of its own than it is of "preventive war" against a country that may, some day, pose a challenge to another state. That is seen more as an act of raw power than of self-defense.