A “Liberal Leviathan.” According to political scientist G. John Ikenberry, that is the role played by the United States since the end of World War II, postwar settlements being by definition “ordering moments” with a “quasi-constitutional function” (38). The US has thus presided over (and led, if not dominated) a liberal, although not global, hegemonic order: “a hierarchical order with liberal characteristics” with a “distinctive blend of command and reciprocity, coercion and consent … more hierarchical than anyone expected, but … also more institutionalized and infused with a complex array of bargains and agreements” (3, 207).

This order – Ikenberry argues – was based upon several preconditions, which help explain its uniqueness, duration and ultimate success. It has been an integrative order, where the hegemonic state – the United States – has led through an effective combination of command and consent. Consent was achieved through the creation of effective mechanisms of governance: a set of rules and institutions capable of being, simultaneously, “tools of hegemonic power and constraints on the exercise of that power” (102). Furthermore, the hegemon has been willing to restrain its crude power, and strengthen the consensus on its leadership, by guaranteeing “voice opportunities” (i.e. “channels and networks for reciprocal communication and influence” – 72) to its subordinate allies and by offering them “public goods” such as security and open trade. However, power, while restrained, has also played a role. The order was hegemonic because it recognized the distribution of power in the international system and reflected the consequent hierarchy among its members. The United States was not just, or simply, a liberal hegemon. It was also a Leviathan: willing to operate within the restraints imposed by the set of rules and institutions it contributed to build, but also dominant, and prepared, when needed, to organize and enforce order. The US has paradoxically become more powerful as a consequence of its capacity to contain and limit its power. “If the leading state can bind itself and institutionalize the exercise of power, at least to some credible extent, offering to do so becomes a bargaining chip it can play as a way to obtain the institutional cooperation of other states” (99).

By avoiding a coercive use of its power, by providing public goods, and by fostering institutionalized mechanisms of governance, the United States has been able to transform its primacy into a form of consensual hegemony far different and more effective than traditional varieties of imperial domination that were markedly more crude and naked in their intent. In the postwar order, US hegemony has often manifested itself as “rule-based leadership … built around multilateral rules and institutions” (84). Because of its very nature, US hegemony – Ikenberry claims – has been bestowed with a level of legitimacy which empires can only aspire to. “Power and rules” – Ikenberry writes in a telling footnote which neatly summarizes his argument – “are not the opposite but work together in complex and reinforcing ways” (85). A problem arose, however, in the transition from a bipolar to a unipolar system, following the collapse of the Soviet Union and the end of the Cold War. Most predictions notwithstanding, the future did not imply a return to traditional forms of multipolar antagonism and balancing; the US did not decline; counterhegemonic coalitions were not formed; civilizations did not clash. The post-1945 American-led world order did not crumble; it was consolidated and further expanded to possibly include the entire globe. The victory, however, was less sweet than expected. The post-1945 hegemonic bargain proved more difficult to preserve. The legitimacy of US hegemony was challenged; preserving the conditions that made this hegemony possible became increasingly difficult, both at home and abroad. The US could not play the role of the balancer any more, since there was no alternative pole – the USSR – that needed be balanced and contained. Within the United States there were fewer incentives to cooperate, abide by the rules, operate within international institutions, and not exploit the immense power gap between the US and the rest. The imperial temptation, as the years of Bush at the White House clearly showed, was simply too hard to resist. “Unipolarity,” Ikenberry writes, “leads to demands by the lead state to be treated differently, and this reduces its willingness to operate within multilateral rules and institutions” (245). The last part of the book is thus dedicated to the “failure of the Bush revolution” (270) – an unrealistic and self-defeating shift from liberal hegemony to empire, where “America rules the world but does not abide by rules” (270) – and to the necessity to rethink and renew the liberal order, making it more inclusive and, overall, less hierarchical and US-dominated.

Occasionally (and annoyingly) redundant and pleonastic as only IR treatises seem capable of being, Liberal Leviathan is nevertheless a challenging and well-argued book that historians of US foreign relations can ignore only at their peril, especially given Ikenberry's influence in the public debate. While building upon his previous works – particularly After Victory (2000) and the various essays on the post-9/11 radical shift of the Bush administration – Ikenberry here pushes his argument well beyond his past writings, better qualifying some of the inner limits and contradictions of the US-led liberal order and discussing the objective dilemmas of post-Cold War US foreign policy, Bush's and neoconservatives’ follies notwithstanding.

Still, some of the arguments and assumptions of Liberal Leviathan are difficult to accept, particularly for Cold War historians. For reasons of space I shall limit my criticism here to three main aspects of Ikenberry's analysis. The first is the artificial distinction between empire and hegemony that runs through the pages of the book. In Ikenberry's simplistic algebra, there are two elementary equations: coercion = empire; and consent/restraint = hegemony. One wonders where the place of liberal imperialism, British and American, is, and why, to put it simply, an empire cannot also be hegemonic. Empires, and successful ones, have always operated through the very combination of coercion and consent, force and trade-offs that Ikenberry attributes to the uniquely benign liberal order of US hegemony. The second criticism is of the rigid periodization adopted by Ikenberry. A growing number of historians have been questioning the idea of using the standard Cold War beginning and end dates as periodizing turning points. Scholars of US foreign relations have increasingly emphasized the importance of the 1970s – the end of Bretton Woods, post-Vietnam, unilateralist/neoconservative turn etc. – in the rethinking and relaunching of a new, and possibly frailer, form of US hegemony. By focussing so much, and exclusively, on 1991 and post-Cold War unipolarity, Ikenberry fails to discuss recent historiography, which is all the more disappointing given his ability in the past to engage in a dialogue with historians as few IR-ers have been willing or capable of doing. Finally, the self-restraint of the United States is greatly exaggerated. Ikenberry tends to take the first years of post-1945 US–European relations and make them into a sort of paradigm of US foreign-policy behavior broadly. Despite occasional references to the different attitude of the United States vis-à-vis Asian and Latin American friends and enemies, the highly institutionalized transatlantic relationship is taken as a model and universalized as an international order. But even in the quite peculiar transatlantic order, the US has played by the rules when it has found it convenient and useful to do so, and has rejected (or rewritten) those very rules when they were useless or dangerous. And this began well before the post-Cold War unipolar turn, John Bolton, the International Criminal Court, and the Bush doctrine. Again, the 1970s and the 1980s offered various examples, from monetary policies to rearmament and missile defense (not to mention attacks on the United Nations and Reagan's hypernationalism). The temptations of unipolarism, in other words, came well before the collapse of the Soviet Union made unipolarity a reality. This otherwise intelligent and important book does not, however, explain why.