Our armies do not come into your cities and lands as conquerors or enemies, but as liberators. ... It is [not] the wish of [our] government to impose upon you alien institutions. ... [It is our wish] that you should prosper even as in the past, when your lands were fertile, when your ancestors gave to the world literature, science, and art, and when Baghdad city was one of the wonders of the world. ... It is [our] hope that the aspirations of your philosophers and writers shall be realized and that once again the people of Baghdad shall flourish, enjoying their wealth and substance under institutions which are in consonance with their sacred laws and their racial ideals.

-- General F. S. Maude to the people of Mesopotamia, March 19, 1917

The government of Iraq, and the future of your country, will soon belong to you. ... We will end a brutal regime ... so that Iraqis can live in security. We will respect your great religious traditions, whose principles of equality and compassion are essential to Iraq's future. We will help you build a peaceful and representative government that protects the rights of all citizens. And then our military forces will leave. Iraq will go forward as a unified, independent, and sovereign nation that has regained a respected place in the world. You are a good and gifted people -- the heirs of a great civilization that contributes to all humanity.

-- President George W. Bush to the people of Iraq, April 4, 2003

It is fast becoming conventional wisdom that the power of the United States today closely resembles that of the United Kingdom roughly a century ago. In the conclusion of my latest book, I attempted a brief comparison between British and American imperial rule, and I am far from the only historian to think along these lines: both Walter Russell Mead and Joseph Nye have also alluded to the continuities in their recent work.

Indeed, the two empires have many superficial similarities. Take Iraq. As the epigraphs show, President Bush, when he addressed the Iraqi people on television shortly after the United States seized Baghdad earlier this year, unmistakably (although no doubt unconsciously) echoed the rhetoric used by the British commander who occupied the city in 1917. And the similarities are not limited to language. In both cases, Anglophone troops swept from the south of Iraq to Baghdad in a matter of weeks. In both cases, their governments disclaimed any desire to rule Iraq directly and hastened to install a government with at least the appearance of popular legitimacy. In both cases, imposing law and order proved harder than achieving military victory (the British had to use air power to quell a major insurrection in the summer of 1920). And in both cases, the presence of substantial oil reserves -- confirmed by the Anglo-Persian Oil Company in 1927 -- was not a wholly irrelevant factor, despite protestations to the contrary.

Nevertheless, whereas the British were generally quite open about the fact that they were running an empire, few American politicians today would use the "e" word as anything other than a term of abuse. As the military analyst Andrew Bacevich has noted, this goes for both Democrats and Republicans. Speaking in 1999, Sandy Berger, President Clinton's national security adviser, declared that the United States is the "first global power in history that is not an imperial power." A year later, then candidate George W. Bush echoed his words, arguing, "America has never been an empire. ... We may be the only great power in history that had the chance, and refused." Reverting to this theme aboard the U.S.S. Abraham Lincoln on May 1 this year, President Bush insisted, "Other nations in history have fought in foreign lands and remained to occupy and exploit. Americans, following a battle, want nothing more than to return home." A few days previously, Defense Secretary Donald Rumsfeld had picked up the refrain in an interview with al Jazeera, when he claimed, "We're not imperialistic. We never have been."

Americans, in short, don't "do" empire; they do "leadership" instead, or, in more academic parlance, "hegemony." That is the concept that needs to be employed, therefore, to make any systematic comparison between the British and the American experience of overseas power. Presciently, in 1997 the British economic historian Patrick O'Brien and the Luxembourg scholar Armand Clesse invited a collection of eminent scholars to undertake just such a comparison. The resulting book, belatedly published last year, has not received the attention it deserves. Among the 18 contributions are some of the most rigorous pieces of work yet published on a subject that is as important as it is topical.

EMPIRE BY ANOTHER NAME

What is this thing called hegemony? Is it a euphemism for "empire," or does it describe the role of a primus inter pares, a country that leads its allies but does not rule subject peoples? And what are the motives of a hegemon? Does it exert power beyond its borders for its own self-interested purposes? Or it is engaged altruistically in the provision of international public goods?

According to S. Ryan Johansson, one of the contributors to Two Hegemonies, the word "hegemony" was used originally to describe the relationship of Athens to the other Greek city-states that joined it in an alliance against the Persian Empire. "Hegemony" in this case "mean[t] that [Athens] organized and directed their combined efforts without securing permanent political power over the other[s]." By contrast, according to the "world-system theory" of Immanuel Wallerstein, the book's final contributor, "hegemony" means more than mere leadership but less than outright empire. A hegemonic power is "a state ... able to impose its set of rules on the interstate system, and thereby create temporarily a new political order." The hegemon also offers "certain extra advantages for enterprises located within it or protected by it, advantages not accorded by the 'market' but obtained through political pressure."

Yet another, narrower definition is offered by Geoffrey Pigman, in his introduction to a useful and original chapter in Two Hegemonies on agricultural trade liberalization in the 1990s. Pigman describes a hegemon's principal function as underwriting a liberal international trading system that is beneficial to the hegemon but, paradoxically, even more beneficial to its potential rivals. Pigman traces this now widely used definition of the word back to the economic historian Charles Kindleberger's seminal work on the interwar economy, which describes a kind of "hegemonic interregnum." After 1918, Kindleberger suggested, the United Kingdom was too weakened by war to remain an effective hegemon, but the United States was still too inhibited by protectionism and isolationism to take over the role. This idea, which became known, somewhat inelegantly, as "hegemonic stability theory," was later applied to the post-1945 period by authors such as Arthur Stein, Susan Strange, Henry Nau, and Joseph Nye. In this literature, the fundamental question was how far and for how long the United States would remain committed to free trade once other economies -- benefiting from precisely the liberal economic order made possible by U.S. hegemony -- began to catch up with it. Would Americans revert to protectionist or mercantilist policies in an effort to perpetuate their hegemony, or stick with free trade at the risk of experiencing relative decline? This is what Stein called "the hegemon's dilemma," and it appeared to him to be essentially the same problem faced by the United Kingdom before 1914. Paul Kennedy drew a similar parallel in his influential The Rise and Fall of the Great Powers.

THE BRITISH MYTH

Having defined "hegemony," the next question becomes which of the two states, the United Kingdom or the United States, was more hegemonic? In the book's introduction -- a tour de force of truly magisterial scope and penetration -- O'Brien gives an unequivocal answer: the United States. To be sure, the United Kingdom had a moment of "hyperpower" in the immediate aftermath of the Napoleonic Wars, when, as one Prussian general noted, it was "mistress of the sea. ... Neither in this dominion nor in world trade has she now a single rival to fear." Yet the United Kingdom was never truly hegemonic in the century that followed. The "Pax Britannica" depended mainly on the Royal Navy, O'Brien explains, "and was therefore bound to be far more constrained than the 'penetrative' military power which allowed governments ... in Washington to become really 'hegemonic.'" For a century, with the sole exception of the Crimean War, the United Kingdom avoided military interventions, preferring to "placate the sensitivities and political antagonism of European governments."

Moreover, the international spread of free trade and free navigation -- the "public goods" most commonly attributed to the British Empire -- were as much spontaneous phenomena as they were direct consequences of the United Kingdom's power. Indeed, when "neomercantilism" reared its baleful head in the later nineteenth century, the empire actually acted as "an impassable barrier to the formulation of a clear and effective strategy" that might have otherwise preserved the "liberal international order." Likewise, the spread of the gold standard was achieved "more by example than by any exercise of authority"; "the diffusion of gold simply evolved at its own pace." O'Brien is dismissive of the idea that the Bank of England was an "agency of Britain's hegemony before 1914." In short, he sees British hegemony as a "myth." Also unfounded is the idea of "two interconnected and evolving hegemonies" linking the United Kingdom and the United States in a line of "hegemonic succession." Such notions, O'Brien mischievously concludes,

[have been] propagated by historians and social scientists [as] part of the cultural foundations of a prolonged and now indisputably unprofitable special relationship (of Greece to Rome, as Macmillan suggested to Kennedy) pursued by British political elites since the War.

John Hobson, another of the book's contributors, broadly shares O'Brien's view of the British Empire. According to Hobson, the era of free trade supposedly engineered by British hegemony came a good 45 years after the post-Napoleonic zenith of British military power and was in any case short-lived. As with the decision to join the gold standard, countries took the decision to adopt free trade for reasons of their own, not because London forced them to. In any case, by the time free trade and gold had become widespread, the United Kingdom's military power was far from hegemonic. This was not a function of incipient economic decline induced by imperial overstretch. In reality, the British Empire was (in the words of the international political economist Susan Strange) "comparatively cheap to run," and before 1914, "the British taxpayer was actually undertaxed relative to the nationals of rival great powers." Hobson calculates that the British "military burden" between 1870 and 1913 averaged a mere 3.2 percent of net national product; by contrast, the figure for the United States between 1950 and 1974 was 9 percent -- nearly three times higher. The British problem was not one of resources, then, but of political will. As the Princeton historian Aaron Friedberg argued some 15 years ago, "with a larger, more capable and more readily expandable army, the British might have been able to indefinitely deter a German assault on France [or at least] to have played a decisive role in the early stages of the continental conflict." Alternatively, they might have opted to appease the Kaiser's Germany, leaving France to her fate. Instead, British politicians chose the worst of both worlds, committing themselves to a war against Germany for which they were militarily unprepared and that they could only win at a crippling cost and with considerable assistance from the United States.

Hobson shrewdly points out a contradiction within the work of Paul Kennedy. Kennedy's argument in The Rise and Fall of the Great Powers -- that the United Kingdom had been overstretched before 1914 (and, famously, that the United States might be in the same predicament today) -- conflicts with Kennedy's other work, in which he has acknowledged the relative lightness of the United Kingdom's imperial burden. Rather than refuting Kennedy, however, Hobson seems chiefly interested in postdating the era of overstretch. In a characteristically combative essay, Correlli Barnett restates his well-known thesis that by the 1920s "the British Empire was one of the most outstanding examples of strategic overextension in history," and that this overstretch had profound and deleterious economic consequences. The logical inference from his and Hobson's chapters is that the United Kingdom's overstretch was a consequence of the First World War, whereas its understretch was among the war's causes.

According to O'Brien and Hobson, the situation is very different in the case of the United States, which, for over half a century now, has represented (in O'Brien's words) "the sole example of geopolitical hegemony since the fall of Rome." As he explains, Hegemony appeared when a young, extremely well-endowed state, after just a century or more of relevant experience in successfully managing the colonization of a largely uninhabited continent, of assimilating diverse ethnic and religious populations into a nation with a self-confident and homogeneous identity, decided to take on the task of creating external conditions for peace and prosperity, primarily for its own capitalists, but by extension for the rest of the world itself.

The authors' argument about the uniqueness of American hegemony rests on four main pillars. The most obvious is economic: as they point out, the U.S. economy has outstripped almost all of its competitors for much of the past century. This point is developed by another of the book's contributors, Angus Maddison, and explored in almost encyclopedic depth in the chapter by Moses Abramovitz and Paul David. According to these authors, nothing achieved by the United Kingdom -- not even in the first flush of the Industrial Revolution -- ever compared with the United States' recent economic predominance.

Second, the authors point to the way the United States has very deliberately used its power to advance multilateral, mutually balanced tariff reductions under the General Agreement on Tariffs and Trade (later the World Trade Organization). As Robert Gilpin argues in his chapter, the tariff reductions achieved in the 1967 Kennedy Round negotiations (and subsequently) owed much to "American pressures." Such pressure was classically exerted through "conditionality" -- that is, the terms under which the Washington-based International Monetary Fund granted its loans. This deliberate process contrasts markedly with the willy-nilly way free trade spread in the nineteenth century, as described by O'Brien and Hobson.

The third pillar of American dominance can be found in the way successive U.S. governments sought to take advantage of the dollar's role as a key currency before and after the breakdown of the Bretton Woods institutions, which, according to O'Brien, enabled the United States to be "far less restrained ... than all other states by normal fiscal and foreign exchange constraints when it came to funding whatever foreign or strategic policies Washington decided to implement." As Robert Gilpin notes, quoting Charles de Gaulle, such policies led to a "hegemony of the dollar" that gave the U.S. "extravagant privileges." In David Calleo's words, the U.S. government had access to a "gold mine of paper" and could therefore collect a subsidy from foreigners in the form of seigniorage (the profits that flow to those who mint or print a depreciating currency).

Finally, although this point gets much less attention than the others, U.S. hegemony has also resulted in some part from the way the country has led, for half a century now, a "formally constituted alliance of states" -- namely NATO -- "committed ... to the containment of two rival superpowers."

THE RELUCTANT READER

As the above suggests, the majority view that emerges from Two Hegemonies is that recent history has only known one hegemon: the United States. At a time when the world is as awed by American "hyperpower" as it is bored by British "minipower," the conclusion is no doubt seductive. But is it correct?

The authors' answer is not entirely convincing, thanks in part to several links missing from this volume -- omissions that are perhaps inevitable for an effort cobbled together by 18 scholars from diverse disciplines. One assumption that goes largely unchallenged is that there is some direct correlation between productivity growth rates and hegemony. The authors seem to ignore the evidence that the United States has not suffered any material diminution of its hegemonic position since 1950, despite the fact that most European and East Asian economies have achieved much higher rates of productivity growth since then. As Angus Maddison said during the conference that inspired this book, "to become a successful hegemon, it helps to be both very rich and very big." But the United Kingdom was neither when it embarked on its imperial enterprise in the early seventeenth century, whereas India, which became a British dependency, was both. The United States is rich and big today, but so are Japan and Germany, which nevertheless remain geopolitical pygmies. The deterministic economic assumptions that underlie so much "hegemony theory" deserve to be challenged; unfortunately, this book does not do it.

In rather the same way, its authors tend to exaggerate the importance of systems of fixed exchange rates. Was the Bretton Woods structure, for example, really so important to the United States? De Gaulle thought so, of course, but he was hardly a neutral economic analyst. From quite an early stage, the system came to depend on legislative restrictions on American capital exports (John F. Kennedy's Exchange Equalization Act), and by the early 1970s, maintaining gold convertibility looked to many like an anachronistic constraint on U.S. growth. In any case, American power can scarcely be said to have waned significantly since the advent of fiat money (that is, currency not backed by gold or silver) and floating exchange rates. The dollar remains the world's main reserve currency today. And the United States is, in many ways, just as economically and militarily powerful as it was before 1971 (when President Richard Nixon closed the gold window), if not more so.

O'Brien's rejection of the idea of hegemonic succession also seems at odds with well-documented reality: the fact that many British policymakers (and some of their American counterparts) fully expected the United States to take on at least some of the "weary Titan's" global burdens as British power waned. In his chapter in Two Hegemonies, the British historian Anthony Howe quotes a letter from the British free trader Sir Louis Mallet to his fellow liberal, the American David Ames Wells, in which Mallet argued that the American adoption of free trade would: determine the course of human progress during the next century. ... Any such event... would have an enormous retentissement [repercussion] in Europe. Freed from its present fetters, your trade and industry would assume proportions which would make them the dominant factor in the commerce of the world.

That was in 1885. By 1941, U.S. Secretary of State Cordell Hull was just one of many influential figures in Washington to acknowledge that "the trade policies of the British Empire during the latter portion of the nineteenth century ... contributed enormously to the sane and prosperous condition of the world." And by 1945, key figures around President Franklin Roosevelt had been converted to the idea that the United States had to perform an analogous role in the postwar era.

Two Hegemonies also seems to overlook the small matter of will. Calleo rightly notes "a strong diffidence toward exercising world leadership ... as a continuing element in American political culture." This was never a handicap for the British. To be sure, there were always domestic critics of the way the empire was run, from Edmund Burke to George Orwell. But the ideology of imperialism -- the sense of a British mission to rule -- was remarkable for its longevity. It can be discerned even in the Elizabethan period, before an empire had been acquired, and it did not really expire until the humiliation of the Suez Crisis.

Many Americans, on the other hand, have always been reticent about their nation's global role. This reluctance limits the potency that O'Brien, Hobson, and others attribute to the United States and helps explain its distinctly mixed record as a hegemon. How else to account for the many ignominious retreats, from Havana to Saigon to Beirut? Between 1846 and 1914 -- the period when the British claim to hegemony seems most plausible -- the United Kingdom too suffered a few reverses, of course. But not one went unavenged.

Perhaps the book's real problem is that the very concept of "hegemony" is really just a way to avoid talking about empire, "empire" being a word to which most Americans remain averse. But "empire" has never exclusively meant direct rule over foreign territories without any political representation of their inhabitants. Students of imperial history have a far more sophisticated conceptual framework than that. During the imperial age, for example, British colonial administrators such as Frederick Lugard clearly understood the distinction between "direct" and "indirect" rule; large parts of the British Empire in Asia and Africa were ruled indirectly, through the agency of local potentates rather than British governors. A further distinction was introduced by the British historians Jack Gallagher and Ronald Robinson in their seminal 1953 article on "the imperialism of free trade," in which the authors showed how the Victorians used naval and financial power to open markets well outside their colonial ambit. There is an important and now widely accepted distinction between "formal" and "informal" empire. The British did not formally govern Argentina, for example, but the merchant banks of the City of London exerted such a powerful influence on that country's fiscal and monetary policy that its independence was heavily qualified.

A more sophisticated definition of "empire" would have allowed the book's authors to dispense with the word "hegemony" altogether. Instead, they could have argued that the United States is an empire -- albeit one that has, until now, generally preferred indirect and informal rule. (Whether its recent invasions of Afghanistan and Iraq presage a transition to more direct and formal imperial structures remains to be seen.)

The reason the choice of terms matters is that to compare, as the authors do, the United States and the United Kingdom as hegemonies is to miss differences that become obvious when the two are compared as empires. It is certainly true that in economic terms, the United States accounts for a much higher share of global output than the United Kingdom ever did, and it is also true that in military terms, the United States enjoys a greater lead over its rivals (one even bigger than that enjoyed by the United Kingdom immediately after 1815). But in other respects, the two countries' positions are reversed. A century ago, the United Kingdom's formal empire was very large indeed, covering nearly a quarter of the world's surface and ruling roughly the same proportion of its population. Today, on the other hand, the United States' formal empire includes just 14 dependencies (of which the largest is Puerto Rico) and covers less than 11,0000 square kilometers. A century ago, the United Kingdom could draw wealth and personnel from the 15 million of its subjects who had settled in the temperate zones of the empire. Today, by contrast, fewer than four million Americans reside abroad, and nearly all of them live in Canada, Mexico, or Western Europe. A century ago, the United Kingdom was a net exporter of capital, on such a scale that it truly deserved to be called "the world's banker." Today, the United States is a net importer of capital on almost as large a scale. A century ago, British leaders could devote the lion's share of their attention and taxpayers' money to imperial defense and grand strategy, since before 1910, government provided only minimal care for the sick and elderly, and most of that was local. Today, Washington spends its money on social security, defense, welfare, and Medicare -- in that order.

As an exercise in comparative history, then, Two Hegemonies is a curiously skewed work. It spends much more time on trade and monetary policy than it does on the civil and military structures that allow power to be directly exerted. If Joseph Nye is right to think of international politics as a game of three-dimensional chess, then most of the players assembled by this book seem trapped on a two-dimensional board. "Hegemonic stability theory" has offered helpful insights into the way that economic power works. But its neglect of the military and cultural aspects of power leads it to overestimate the current American empire and to underestimate the power of its British predecessor.