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.