Underlying the debate over the aftermath of the Iraq war is a question that, in the long run, looms larger than all of the others: Is President Bush’s foreign policy making Americans safer — or less safe — from the danger of being obliterated by nuclear-armed terrorists?

The answer may be that the Iraq war made us safer but Bush’s continuing scorn for world opinion — manifested by his defiantly uncompromising September 23 speech to the United Nations — is making us less safe. Bush may have been the right president to begin taking the fight to our terrorist enemies and to rogue regimes that seek nuclear arms. Whether he is the right president for the next phase is another question.

The past few months have been daunting for those of us who have hoped that deposing Saddam would deter other rogue regimes from going nuclear. The continuing carnage in Iraq, the unexpected strain on our armed forces, the damage done to Bush’s credibility by his and his aides’ exaggeration of the Iraqi threat and lowballing of the costs of occupation — all cast doubt on the president’s ability to muster the military muscle and the public support to launch another major war if necessary to prevent another rogue regime from going nuclear. And the rogue regimes know this.

So Bush may have exhausted whatever advantage there once was in his my-way-or-the-highway message to the rest of the world. It was one thing to cast aside the vexing constraints of multilateralism when necessary to depose Saddam’s regime. It is something else to insist on a U.S.-British monopoly of power in Iraq, and spurn the compromises necessary to win international support elsewhere, now that we so clearly need help.

The first test of whether the U.S. invasion of Iraq will deter other rogue states from pursuing their nuclear ambitions is taking place right now in Iran. (It may already be too late to deter North Korea, which has millions of South Koreans under its guns and probably possesses at least two nuclear bombs.) If Iran, a charter member of the "axis of evil," continues its long-standing race to build nuclear weapons — if, for example, it defies the October 31 deadline set by the International Atomic Energy Agency for allowing full inspections of its nuclear sites — will Bush be able to scare Iran into backing off?

Or might the mullahs correctly calculate that, with the U.S. armed forces overstretched in Iraq and many Americans unwilling to support another pre-emptive war, the president could not launch a major attack anytime soon? And that the best way to deter any future U.S. attack would be to accelerate their nuclear program?

The worthy vow around which Bush has built his foreign policy is that the United States "will not permit the world’s most dangerous regimes to threaten us with the world’s most destructive weapons." Perhaps he can still make good on that vow. The IAEA’s newly tough posture on Iran may be a reflection of Bush’s own toughness. "It is precisely because we have shown we are willing to go to war that options short of war may now be available to us and to others," asserts one administration official.

And the Iranian tyrants might hesitate to call the bluff of a president who has deposed two terror-sponsoring tyrannical regimes in two years, killed or captured many Qaeda and Baathist leaders, forced the rest into hiding, and stationed the world’s most awesome military force on Iran’s doorstep.

But if Bush proves unable to stop Iran (and North Korea) from going nuclear, his pre-emption doctrine will be a spent force. This would give a green light to the nuclear ambitions of other rogue regimes (Libya, Syria) and of unstable states where militant Islamists may someday seize power (Algeria, Egypt, Indonesia, Saudi Arabia, and more). As the number of nuclear-armed states increased, so would the risk that one of them — gambling that its anonymity would prevent retaliation — might hand off a bomb to terrorists.

If Bush cannot stop Iran, then the last, forlorn hope for stemming the tide of nuclear proliferation would be to bolster the very international institutions and agreements that this administration has so often scorned, including the Nuclear Nonproliferation Treaty and the IAEA. The best way to do that, and to repair the damage done to our security by Bush’s many affronts to world opinion, would be to offer concessions that this president has adamantly ruled out, such as pledging not to develop a new generation of nuclear weapons or to resume nuclear testing.

This does not mean that Bush was wrong to invade Iraq. Whatever else happens, the world is less dangerous than if he had backed down and allowed Saddam to resume his nuclear and biological weapons programs. And that’s exactly what Saddam would have done once the heat was off, with the help of France and Russia, which would soon have reverted to neutering the U.N.’s inspections regime and circumventing its economic sanctions. The notion that America had reverted to paper-tiger status would have emboldened all of our enemies.

Besides, for all the terrible bloodletting and lawlessness in Iraq over the past six months, the collateral benefits of this war for the Iraqi people have been far greater than has the collateral damage. Whatever mix of motives spurred Bush to risk his presidency by invading, the countless thousands of liberated Iraqis who would otherwise have been murdered by Saddam or starved by U.N. sanctions owe him their lives, and all Iraqis owe him their chance to create a decent government. Bush will deserve great credit for that even if he ends up a one-term president.

But Bush also deserves blame, for putting us all in greater danger by squandering both his own credibility at home and the goodwill abroad that we need to win the war against terrorism.

The justification for any pre-emptive war depends on the magnitude of the threat. And any president who proposes such a war has a duty, once any need for surprise has passed, to level with the American people as to what he knows — and does not know — about that threat.

Based on Saddam’s appalling record, I probably would have supported the Iraq invasion even if Bush had disclosed the CIA’s doubts about the British view that "Saddam Hussein recently sought significant quantities of uranium from Africa," in the words of Bush’s January 28 State of the Union address. And even if Vice President Cheney had not waited six months to make it clear that he misspoke when he said on March 16 that "we believe [Saddam] has, in fact, reconstituted nuclear weapons." And even if the administration had not been so willing to foster the widespread, but probably incorrect, impression that Saddam had a role in 9/11, and so elusive about the costs of rebuilding Iraq. And even if Defense Secretary Donald Rumsfeld had not claimed on March 30, "We know where [Saddam’s weapons] are."

But many others who supported the invasion might have felt otherwise if given a more candid account of the threat. And if Bush announces at some future time that, for example, another massive military attack is necessary — this time to stop Iran from crossing the nuclear threshold — many Americans will not take his word for it. He will have to prove it to us.

As for world opinion, we cannot afford a continuation of Bush’s gratuitous affronts to the United Nations and our one-time allies, or his obdurate refusal to make reasonable compromises to win their support. This pattern extends well beyond Iraq.

Bush was right to resist the unrealistic demands of the Kyoto global-warming treaty — but wrong to trash it so overtly while offering no serious alternative approach. He was right not to submit to the jurisdiction of the International Criminal Court as presently constituted — but wrong to so ostentatiously "unsign" the ICC treaty, thereby insulting those who see it as essential to protecting human rights. He was right to detain and interrogate captured Qaeda terrorists as unlawful combatants — but wrong to flout the 1949 Geneva Conventions by refusing to give the many detainees at Guantanamo who may be innocent civilians any chance to tell their stories to military tribunals. He is right to suspect the French government of incorrigible obstructionism — but wrong to alienate the many Europeans who want to help us fight terrorism.

The ideal president for these terrifying times would understand when to give ground as well as when to stand firm. Bush does not appear to be that man. Whether his Democratic opponent next year will come closer to the mark remains to be seen.