As Baghdad fell to US-led forces in April 2003, Secretary of Defence Donald Rumsfeld fired out a terse ‘snowflake’ memo to his staff. ‘We also need to solve the Pakistan problem. And Korea doesn’t seem to be going well. Are you coming up with proposals for me to send around?’ It could serve as Rumsfeld’s epitaph. On the day of the 9/11 atrocities, he helped carry the dead out of the Pentagon before telling advisors America should use the emergency to eliminate its enemies. He was impelled by a vision of overwhelming American strength, spearheaded by a transformed US military. Vulnerability and ambition mixed. ‘Sweep it all up’, he said.

Rumsfeld was not alone in his swagger. It echoed all around. It was part of the ‘unipolar moment’, the short period when the US dominated the world without a peer competitor. President George W. Bush vowed to ‘whip terrorism’, and soon, to destroy it. He went to the repertoire of Pearl Harbor, whereby an innocent and sleeping giant, once assaulted, summons its latent strength. As well as bringing out the whip, a wounded superpower sensed a world-historical chance to reshape the globe. While some with bleaker visions of the world believed war would awe rivals, Bush and court intellectuals had messianic visions of a region transformed under America’s aegis. The author of the phrase ‘unipolar moment’, Charles Krauthammer, used it not to caution but to exhort America to democratise the Middle East, an undertaking he called ‘enormous, ambitious and arrogant.’

With the wind of initial success in Afghanistan at their back, Bush’s vulcans turned their eye to Iraq. A growing sense of righteous might impelled the architects of the ‘Bush Doctrine,’ and their visions grew ever more expansive. A strike into the Gulf, taking dead aim at rogue states as the sources of proliferation and terror, would signal US resolve, break the Israel-Palestine deadlock, liberate oppressed populations, reassure despotic allied regimes that ruled them, correct the defects of the Arab-Islamic world, and even defeat evil itself. It would revolutionise and stabilise at the same time, somehow.

Whatever else drove the will to war, the Bush administration sensed it could. If they could get the politics right, war would work, quickly, cheaply and overwhelmingly. The assumption of a lightning strike, at minimal cost, with an orderly and bloodless aftermath meeting minimal resistance, informed much of the preparation. This was broader and deeper than one faction. The swagger was bipartisan. Regime change was a long-held consensus. Lawmakers of both parties, asked to authorise force, endorsed it almost casually. Most Democrat critiques were procedural and tactical. Before casting their votes, only a handful bothered to visit the Capitol Hill repository to read the CIA’s classified estimate of Saddam’s WMD programme. Under the mandate of heaven, who needs details?

An intoxicating idea ran amok, that America’s success, as a great republic and global hierarch, reflected its sapience. Washington had discovered – its National Security Strategy insisted – that democracy was the universal template of success. Being blessed, and being right, made it invincible. At his ranch, Bush assured Spain’s Prime Minister Jose Aznar, ‘We will be in Baghdad by the end of March…We can win without destruction…I am optimistic because I believe that I am in the right.’ Struck by militant Islamists in its nerve centre, it felt its vulnerability and, paradoxically, exalted in its power. As invasion loomed, a Vice-Admiral yelled to a stomping, cheering crowd of sailors, ‘You are going to bring freedom to a country of millions of people who have been long oppressed!… It’s hammer time.’

As US forces swept into Baghdad, American officials triumphally declared big systemic effects that were at hand, ‘to reshape the Middle East’, as victory ‘opens all sorts of new opportunities for us.’ The US would use victory to educate and coerce rogue states Iran and Syria. Even Secretary of State Colin Powell, ever curating his reputation for multilateralist humility, couldn’t resist strutting. There was ‘no war plan right now’ for the two rogue regimes athwart Iraq, he said, and threatened to punish France for its opposition. In his choreographed declaration of the end of combat operations on the flight deck of the USS Abraham Lincoln, Bush included caveats and wasn’t responsible for the ‘mission accomplished’ banner. But triumphant finality was the clear note. America was having a unipolar moment. Such moments are rare, and because they invite self-defeating behaviour, relatively brief.

What were the sources of this swagger? Lively minds often explain this by looking inward, to the domestic roots of imperial overstretch, both strains of thought and historical experience. In America’s case, they point to a missionary impulse, older ideas of exceptionalism, and/or memories of failed isolationism in the 1930’s. Likewise, it is an article of faith, today, that we can only understand Beijing’s bid for hegemony by excavating its inner history. Locally-rooted impulses, in this picture, are causally prior to a state’s outward behaviour.

But could it be the other way around? Consider an alternative proposition: narcissistic world views primarily derive from the changing distribution of international power. ‘Unipoles’ are those powers that command significantly more capabilities than any other, face no first-order competition, and expect this state of affairs to last for decades at least. Most states who amass such power will want to throw it around, seeing themselves as lords of the horizon. Accordingly, they will find in their past the memories, images and identities to feed it.

At the apex of its global pre-eminence in 2003, Washington lunged into the heart of the Middle East not just out of fear, but because it was a large state with unparalleled wealth and force. This was before the coming of a large, rich peer competitor in Asia, and the global financial crisis. America’s rapid growth, and the cumulative effect of low-cost, successful wars and operations from Iraq in 1991 to Bosnia in 1995 to Kosovo and East Timor in 1999 encouraged a two-party faith that the main problem was a not enough power projection. This tracks with the growing bellicosity of Richard Holbrooke, the Democrat diplomat for whom Bosnia demonstrated America’s capacity, and Eliot Cohen, a Republican historian and strategist. A decade earlier, Cohen defended Bush I’s short, bounded war against Iraq as a prudential exercise in limitation, as Dick Cheney had done. Now, the shackles were off. ‘Iraq can’t resist us.’

Remove America’s experiences, geography and memories, locate other ascendant powers, and a similar thought pattern emerges. By no means do unipoles function identically, and they vary in their brutality and modes of rule. But in their ascendancy, they have comparable hubristic ‘moments’ and similar thought patterns about themselves and their relationship with the world. In particular, their myth-historical self-images share four common elements: a fragile beginning, a period of victimhood, a rebirth during emergency, and a rapid and predestined rise. These unexceptional world views are underpinned, ironically, by a belief in their own singularity. As Edward Said noted, ‘Every single empire in its official discourse has said that it is not like all the others, that its circumstances are special.’ Many are chosen.

Two other unipoles, one ancient and one medieval, echo the pattern. Achaemenid Persia was a universe away from modern America. But in 480 BC, as Xerxes its king mobilised a vast invasion force against peripheral upstarts in Greece, it too fell prey to a unipolar moment. It grew contemptuous of limits. Xerxes’ father, Darius, claimed that as appointee and agent of the god Ahura Mazda, his rightful kingdom was the cosmos itself. Insurgent revolt by Greek city-states in Ionia were an affront to the will of heaven, and helped prompt Xerxes’ grand offensive. For the dominant power, revolt was an offence against goodness, and war the punishment of wickedness. To launch the expedition into Europe, the Persians built two pontoon bridges to traverse the strait and yolk both continents. When a storm wrecked the platforms, the King of Kings had the disobedient Hellespont whipped three hundred times. Like the Hellenic rebels, nature itself was to feel the scourge.

The Achaemenid dynasty cultivated a myth-history about its ascent to global dominion in a familiar sequence: a struggling origin, divine appointment, a rapid rise to pre-eminence, and a predestined and radiant future. As Tom Holland’s imperishable history tells it, ‘their aura of invincibility reflected the unprecedented scale and speed of their conquests. Once, they had been nothing, just an obscure mountain tribe’ in southern Iran, before seizing an empire from India to the Aegean in two generations. Such a lopsided distribution of power, created so quickly, followed by others bandwagoning to it, led Persian to form a cosmology of natural, righteous and universal rule, demanding obeisance everywhere. It travelled badly in the Balkans. Not for the last time there, resolute enemies, harsh geography and bad luck bloodied the nose of an imperious conqueror. Aeschylus, a veteran of the subsequent great naval battle at Salamis that wrecked Persia’s naval force and dented Xerxes’ dreams, wrote a drama dwelling not on the victors’ glory but the suffering of the defeated. His play, The Persians, warned a triumphant Athens about what empire-building could inflict. Power-driven self-regard is a universal disease.

China’s Ming Dynasty (1368-1644) was a colossus on most measures. Its unipolarity was longer and more durable than ancient Persia’s hour in the sun, which a certain Macedonian conqueror terminated. It exceeded America’s moment, which lasted only a few decades. For a time, it was so preponderant that today it inspires Chinese nationalists to believe an ascendant Middle Kingdom, running a tributary empire, is the world’s natural state. A style of global imperial vision was its legacy. As late as the nineteenth century, China’s term for foreign relations was ‘barbarian management.’

A widespread romance persists in many quarters, that a peaceable, non-expansionist and Confucian ethos determined Ming China’s behaviour and shaped its noncoercive tributary empire. That romance is politically useful to propagandists for China’s bid for hegemony today, as they peddle the fiction that China is historically innocent of imperial aggression. To be sure, noble ideals about harmonious non-violence and pessimistic advocacy of power politics and force were both present. Only in practice, and especially when China’s power was waxing, a desire to maximise power, coerce the rebellious and receive deference was stronger in the court’s calculations. The Ming dispensation could be haughty in its violence. Its envoys flogged Korean officials to press their demands. There’s that whip again.

Ming China’s collapse took the form not so much of military over-expansion. Rather, in wider circumstances of economic collapse and political infighting, its vanity made it vulnerable to strategic deception. While the Ming state had successfully contained its other rivals, the Mongols and Japan, it had failed to spot the predatory intent of a more subtle rising challenger, the Manchus who hailed from the north-east fringes. Under the guile of the ruler Nurhachi, the Manchus grew their state and their capabilities over three decades while staying under the radar, and persuading Ming rulers of their peaceful intentions. Ceremonial shows of submission at the Ming Court played to a conceit common among unipoles, that the majesty and benevolence of their order moves even potential rivals to kowtow, making counter-balancing unnecessary. As political scientist Yuan Kang Wang writes, ‘When Japan invaded Korea during the Imjin War, Nurhaci offered to send troops to assist the Ming. Although a few Ming officials were suspicious that Nurhaci had revisionist aims, his apparent adherence to the Chinese world order, in the eyes of the Ming court, demonstrated his “sincere submission” and earned him a promotion to the prestigious title of dragon-tiger general (longhu jiangjun).’ A busy hierarch, pre-occupied in crises elsewhere, liked to think a growing state would evolve on its preferred terms, as a responsible stakeholder supporting the existing order. Couldn’t happen now.

It is power and the changing structural environment, above all, that changes countries. Vast power encourages disparate cultures to adopt similar conceits. The more wealth and capabilities states acquire, the greater it transforms their consciousness. We like to think of ourselves, and our countries, as more internally constant than that, with fixed personalities or attributes that national growth merely magnifies. But as John Mearsheimer asks his audiences, would you really remain the same person if I gave you five million dollars? Great powers do not so much project onto the world their prior cultures. They acquire power, develop a theology of exceptionalism, and find in their cultures the resources to tell a self-serving story. Self-serving, and self-deceiving. In Baghdad, Plataea or Beijing, the self-regard and resulting damage accelerates a brutal correction.

And then? Even as its pre-eminence slips away, the unipole’s pathologies can endure. Like the faith that others will easily bend to one’s will, the impulse to believe military campaigns will be quick and triumphant is not a constant, but forever lurking. Today, across the Taiwan strait, two former unipoles, China and America, are on collision course. Unipolarity leaves a trace memory for both. The optimism has died down. Both fear decline. But both retain visions of themselves and their natural dominion derived from a unipolar era. They still expect their prerogatives, and believe or hope that the other will back off. More must be said about the mindsets of former unipoles. But essays, like empires, have their limits.