What has really changed since last September 11? Not very much. Cataclysmic as it was, that event was more like a bolt of lightning that illuminated the essential contours of the international landscape than like an earthquake that reconfigured it. It dramatized, but did not shape, some profound transformations of world politics in the making for at least a decade. These transformations have to do with the nature, distribution and hierarchy of global power. Paradoxically perhaps, September 11 has dramatized the centrality of the United States in the international security system.

The real watershed event, in retrospect, was not September 11, 2001 but Christmas Day 1991 when the Russian Empire-a.k.a. the Soviet Union-committed suicide by self-dissolution. Suddenly, the world was no longer bipolar but unipolar, no longer defined by the titanic U.S.-Soviet struggle but by the presence of a virtually unchallenged No. 1: the United States. Because the Soviet collapse unfolded without war and revolution-unlike the cases of the Czarist, Ottoman, Habsburg, Hitlerian and colonial empires throughout the 20th century-the consequences of this drama took some time to sink in. Act one took place in 1990-91 when the United States masterminded the global coalition that laid low Saddam Hussein-unopposed by the Soviet Union, Europe and China. Acts two and three followed in 1995 and 1999 when the United States took the lead in bombing campaigns against Serbia-again, virtually unopposed. In the most recent act the United States harnessed a global coalition once more, this time against Terror International sited in Afghanistan. The moral of this tale that stretches from Baghdad to the Balkans to Tora Bora is simple: No. 1 in 1992 has become even more so in 2002.

The war in Afghanistan is in some ways a special case, for it exemplifies a revolution in warfare that has thrust American power into a category all of its own. The war was prosecuted from 7,000 miles away, from Central Command in Florida, in almost "real time." It dramatized force projection, logistical, and command, control and intelligence capabilities that no nation has ever before come close to deploying. So novel and effective was the campaign that it might have foreshadowed the end of the post-Hiroshima age, which is to say that so powerful were some of the "conventional" weapons deployed there (like thermobaric bombs) that the function of nuclear devices may be relegated, really once and for all, to deterrence alone.

Though a new twist in the history of warfare, the war in Afghanistan underscores an old point: the United States is not strong because it has nuclear weapons; it is mighty because it can do without them. Indeed, the power gap between No. 1 and the rest keeps growing. The United States now spends on military capabilities ($377 billion for this fiscal year) almost as much as the rest of the world combined. If the Bush Administration adds to the defense budget every year as planned so that, by 2007, the United States will allocate $450 billion, then, ceteris paribus, the United States will outspend all others combined. Not since the days of the Roman Empire has such a power gap between No. 1 and the rest existed.

This was bound to have consequences, and the best shorthand description of the most important of these is the Rumsfeld Doctrine. That doctrine proclaims that "the mission determines the coalition, and not the other way round", and its first victim was nato. Indeed, nato as we have known it for half a century, as an anti-Soviet alliance, is dead. That was nato i, in essence a unilateral American guarantee binding the United States to the defense of Europe. It has been replaced by nato ii, best defined as a collection of states, now including Russia, from which the United States draws coalition partners ad hoc. nato ii, in other words, is a pool, not a pact; accordingly, in nato ii's first war, (some) members acted as chosen handmaidens, not as foreordained beneficiaries, of American might.

This represents a momentous and still insufficiently appreciated change in Atlantic relations, and to grasp the full scope of American pre-eminence the point must be pushed still further. The aftermath of September 11 has certified America's global primacy in terms of both structure and process. No. 1 in the hierarchy of power, the United States is also the foremost impresario of the world's major politico-strategic relationships. America's Cold War alliances with Western Europe and Japan (and briefly cento and seato) were once the single axis around which American grand strategy revolved. They still play prominent roles, but in a system that is now tous azimuts. The proper metaphor is that of "hub and spokes", with America as the hub and players 2, 3, 4, 5 and so on representing the spokes. Who are they?

"Europe" remains a founding member of the system, but as a set of ad hoc participants rather than as a single entity, be it nato or the eu. A privileged European player is Britain, another, though more ambiguously so, is Germany. France is simultaneously an active ally (as in the Balkans or in Afghanistan) and a quondam object of containment. Poland-and indeed all the beneficiaries of the American-led enlargement of nato-as well as Turkey, are useful counterweights against the larger continentals. Europe itself is a regional version of the hub-and-spokes system, with the United States ever so subtly playing some against others, or recruiting posses for the intervention du jour.

Once the very raison d'être of America's Cold War alliances, Russia is the newest spoke in America's global wheel. This does not signify a "reversal of alliances" but it does considerably enlarge America's margin of maneuver. The moment Vladimir Putin dropped Russia's active hostility to missile defense in exchange for drastic nuclear arms control, opposition in Europe and China was all but neutralized. With Putin in the American boat, the war in Afghanistan was enormously facilitated; U.S. bases in Central Asia, the "soft underbelly" of the former Soviet Union, would have remained out of reach if not for Russia's consent. America's bases now stretch around the world: from Norfolk, Virginia via Europe and the Middle East into Central Asia, and from there to the Western and Central Pacific all the way back home to San Diego. By comparison, imperial Britain at its height looks like a poor second cousin to 21^st-century America.

The Middle East is at present a spoke in the making. The United States has not yet imposed peace on the Levant, full discipline on nominal allies like Saudi Arabia, nor yet transformed the regimes of its two major foes, Iran and Iraq. But Ariel Sharon and Yasir Arafat, Riyadh and Cairo, all take their quarrels to Washington and all depend on American might and benevolence. If the United States pulls off its Saddam and Palestinian capers, it will all but complete its quest for dominance over the Middle East initiated with the extrusion of Britain and France after the Suez War of 1956. All that would remain would be the fall of the Islamic regime in Iran.

In the Far East, both large players like Japan and lesser ones like Thailand prefer to huddle under the American umbrella rather than face China on their own. China, of course, is the long-term strategic challenger but, so far, the subtle American mix of containment and socialization are working much better than did its all-sticks/no-carrots strategy toward Japan in the 1930s. At any rate, Beijing has not recruited either Russia or the Western Pacific coastal nations into its own orbit. Along with Australia and New Zealand, these remain regional spokes in America's global wheel.

The historically tutored will notice that this resembles the Bismarckian system on a global scale. Like the Second Reich in Continental Europe then, the United States is No. 1 in the world now-by dint of its strategic centrality, economic dynamism and cultural sway. Yet precisely because of their predominance, each nation has had to find a way to keep numbers 2, 3, 4 et al. from ganging up against No. 1. Bismarck limned the solution in his famous Kissinger Diktat. (1) The task, he wrote in 1877-six years after German unification-was to create a "universal political situation in which all the powers except France need us and, by dint of their mutual relations, are kept as much as possible from forming coalitions against us." Germany thus sought better relations with Britain, Russia and Austria than they might forge among themselves, so to make them "spokes" to Berlin's "hub."

The American system today is Bismarckian writ large, but will it last longer than Bismarck's? That system endured until 1893, when France and Russia concluded an alliance against Germany-or, interpreted more generously, for almost half a century, until 1914, when Germany had to fight a war against almost all of Europe. The United States can do better than that if its grand strategy amounts to more than just playing one "spoke" against the other. The aim should be not only to prevent, but to pre-empt, hostile coalitions by undercutting the reasons for their formation. The point is to make other powers willing participants in the American system.