On Sept. 11, the president was handed a historic opportunity. He ignored it.

Painful as it is to recall those planes smashing into the Twin Towers and the Pentagon two years ago this week, it's nearly as heartbreaking to think back on the moment of nascent harmony that ticked in the wake of the attack—until President Bush decided to reject the opportunity that History thrust before him.

Remember? The French newspaper Le Monde, never one for trans-Atlantic sentimentalism, proclaimed, "We are all Americans." The band outside Buckingham Palace played "The Star-Spangled Banner" during a changing of the guard, as thousands of Londoners tearfully waved American flags. Most significant, the European leaders of NATO, for the first time in the organization's history, invoked Article 5 of its charter, calling on its 19 member-nations to treat the attack on America as an attack on them all—a particularly moving gesture, as Article 5 had been intended to guarantee American retaliation against an attack on Europe.

But the Bush administration brushed aside these supportive gestures—and that may loom as the greatest tragedy of Sept. 11, apart from the tolls taken by the attack itself.

Ever since the crumbling of the Soviet Union, foreign-policy specialists had been wondering how to create a new world order for an era that lacked a common enemy. Now, suddenly, here was that enemy. And here was a moment when the world viewed America with more empathy than it had in the past half-century. An American leader could have taken advantage of that moment and reached out to the world, forged new alliances, strengthened old ones, and laid the foundations of a new, broad-based system of international security for the post-Cold War era—much as Harry Truman and George Marshall had done in the months and years following World War II.

But George W. Bush, Dick Cheney, Donald Rumsfeld, and Condoleezza Rice did not take that path.

Aside from letting a handful of NATO's AWACS radar planes come help patrol American skies, Bush's response was a shockingly terse: Thanks, but no thanks; we'll handle it by ourselves. Marc Grossman, the undersecretary of state for political affairs, later admitted to the Washington Times that the United States initially "blew off" the allies. Douglas Feith, the undersecretary of defense for policy, said that the United States, in the Times' words, "was so busy developing its [Afghanistan] war plans that it did not have time to focus on coordinating Europe's military role."

The effect, of course, was to alienate the allies just as they were rediscovering their affections. As London's conservative Financial Timeslater put it, "A disdainful refusal even to respond to a genuine offer of support from close allies, at the time of America's most serious crisis in decades, spoke volumes about its attitude to the alliance."

As late as a year ago, around the time of the attack's first anniversary, the bloom had not yet entirely worn off. On Sept. 8, 2002, the French president, Jacques Chirac, repeated the words of Le Monde as if they were his own—"We are all Americans"—and added that these feelings "haven't disappeared," that "when the chips are down, the French and Americans have always stood together and have never failed to be there for one another."

Two months laterNATO held a summit in Prague, mainly to expand its membership to include several nations of the former Warsaw Pact, but also to devise what planning documents called "a comprehensive package of measures" to combat terrorism and other threats. Among these measures would be the creation of a "NATO Response Force"—the documents even envisioned an acronym, the "NRF"—consisting of "a technologically advanced, flexible, deployable, interoperable, and sustainable force … ready to move quickly to wherever needed, as decided by the [NATO] Council."

A week before the Prague Summit, Lord George Robertson, NATO's secretary-general, gave a glowing speech about its prospects to the NATO parliamentary assembly in Istanbul. "Prague," he said, would "give us the chance to demonstrate that not only our security environment has changed, but that NATO has changed with it." The summit would confirm that NATO was becoming "the focal point" for the fight against terrorism. And it would "debunk the myth that has crept into the trans-Atlantic relationship after 9/11—the myth that the US and its Allies are no longer able or willing to cooperate as a military team. … It will demonstrate that Europe and America are on the same wavelength—both mentally and militarily."