As questions mount around the failure to find weapons of mass destruction in Iraq and the intelligence that was used to justify going to war, one of the first casualties may be the Bush administration's doctrine of preventive war.
That is just one way the controversy over the use of intelligence to justify war is likely to impact US foreign policy. Already the wisdom of waging war against a gathering but unexercised threat is being questioned in Congress and among weapons experts.
But the failure to find weapons and the clouds over prewar intelligence are also feeding US allies' doubts on the rationale for war, and solidifying opposition to the administration's stated right to preemptive war.
"People who opposed this war feel vindicated and will feel even stronger about the risks of the doctrine of preventive war, that you have to base it on intelligence that may be flimsy, inaccurate, or can be interpreted in different ways," says Jens Van Scherpenberg at the German Institute for International and Security Affairs in Berlin.
Calling the last year "difficult for everybody," a European diplomat in Washington says, "We see validation of the importance of inspections, the priority of cooperation, and we will emphasize that as the right way to go forward." Still, to the extent the administration holds to its first-strike policy even in the absence of a proven, imminent threat, defining differences between the US and some allies will continue.
"There is a lasting schism" between the US and some of its allies over the use of military force, fed by specific differences over defense spending, adds Mr. Van Scherpenberg. But he and others in antiwar countries say the underlying differences, while too deep to go away, will be played down in coming months as Europe seeks to repair relations with Washington, and Washington continues to press for international help in postwar Iraq.
European leaders may be hoping the White House has learned from what they believe are the pitfalls of preemptive military action - a doctrine first outlined in the Bush administration's national security strategy of August 2002.
Some experts argue that British Prime Minister Tony Blair - and even Mr. Bush - will be hesitant to repeat the Iraq venture because of public opposition and political scrutiny. In short, observers note, antiwar leaders may not feel compelled to focus on the doctrine's liabilities since others in Washington already are.
In a televised interview this week, former chief US weapons inspector David Kay said, "If you cannot rely on good, accurate intelligence that is credible to the American people and to others abroad, you certainly can't have a policy of preemption."
And in a speech on the Senate floor Tuesday, Sen. Bob Graham (D) of Florida, former chairman of the Sentate Select Committee on Intelligence, said "if we continue to rely on preventive or pre-emptive military actions as a central part of our strategy, it is critical that we have accurate intelligence to justify that the threat to be preempted is imminent."
The added importance of accurate intelligence when it is being used to justify war, and flaws in intelligence on Iraq, are prompting action on both sides of the Atlantic. Bush this week ordered creation of a commission to examine intelligence shortcomings, and Mr. Blair opted for a similar investigation.
Those steps, and others that US allies see as retreats from a first-strike doctrine, or as "peace feelers" toward them, may improve working conditions between allies.
Also easing tensions are recent statements by Secretary of State Colin Powell, first acknowledging that weapons of mass destruction may not have existed in Iraq, and Tuesday stating in an interview that a clear absence of stockpiled weapons might have affected his recommendation for war. Still, he told the Washington Post that he believed Saddam Hussein's Iraq did have an intent and capability that justified action, and that history would vindicate the war.
At the same time, there is hope in some European capitals that the administration is shifting its emphasis to building alliances.
"France always felt the doctrine of preemptive action was impracticable, and while that view has not changed, the emphasis now is on improving relations with the US," says Philippe Moreau Defarges, an international-relations expert at the French Institute for International Relations.
Washington's emphasis last year on war was seen as deleterious to the sharing of intelligence, since governments disagreed on how intelligence should be used. But Mr. Moreau Defarges says Paris wants to heal relations with Washington and, in turn, improve counterterrorism and international economic policies - so the French government will not make an issue of Iraq at this time.
"Look at the recent cancellation of some commercial flights from Paris to the US," he says. "There a strong signal from the French government saying, 'We want to cooperate.' " Though the French are no more likely to go along with preemptive war, he continues, they feel reassured that the US has reached the limit of its own doctrine. "Look at North Korea: That is a more dangerous threat, but the US is not talking about waging war there."
Indeed, though a tougher stance may be required in North Korea, any action would be made more difficult by doubts about the Iraq war, says David Mepham of the London-based Institute for Public Policy Research. "The chance of getting public support will be reduced," he says. "The lack of credibility brought on by going to war in Iraq on the basis of inaccurate intelligence has undermined public trust and made the world more insecure."
• Mark Rice-Oxley contributed.