For the past decade, at least, the American grand strategy debate has pitted deep engagers and restrainers. Deep engagers and restrainers disagree over whether it is in the United States’ interest to underpin stability, and liberal order more broadly, in core regions like East Asia, Europe, and the Middle East or whether it is more sensible to husband American power in anticipation of a hegemonic challenge in one or more of those regions. If Ionut Popescu is right, that challenge has arrived, in the form of a rising China, which means that the deep engagement versus restraint debate must be superseded by a singular focus on ensuring that “no peer rival” emerges from this era of Great Power Competition (or GPC, to use the Beltway term of art).

No Peer Rivals excels in two respects as a contribution to the American grand strategy debate. First, it roots its arguments firmly in the International Relations theory canon. Popescu’s preferred No Peer Rivals approach follows directly from the tenets of offensive realism, with its emphasis on the struggle for hegemony among great powers. Indeed, Popescu makes the case up front that the United States’ great power rivals, China and Russia, are already acting in an offensive realist fashion, which requires the United States to follow suit. Most importantly, the United States must drop any pretensions that enduring cooperation is possible with a rising China that has hegemonic ambitions. That is what separates Popescu, an offensive realist, from those liberal internationalists and defensive realists who are more optimistic about China’s rise and who generally believe that a mix of cooperation and competition characterizes relations among the great powers. At the same time, Popescu is careful to emphasize that there is less room for ideology in an era of Great Power Competition than otherwise hawkish conservative internationalists are accustomed to. The implications for Russia policy are especially important: the challenge that Russia poses to the liberal international order is less pressing than the nascent alliance it has formed with China. The goal should be to contain Russian expansion in the short term while facilitating Russian neutrality in the US–China competition over the long term.

Second, if grand strategy is about reconciling ends, ways, and means at the highest level, No Peer Rivals is especially effective at providing concrete guidance on what ways and means are required to fulfill its strategic vision. In separate chapters, Popescu outlines the military, economic, and diplomatic requirements of his approach, which cohere together into a comprehensive blueprint for containing China. Militarily, this means preparing for a high-intensity war over Taiwan, as Elbridge Colby lays out in The Strategy of Denial (2021). Economically, it means decoupling from China so as to restore manufacturing and supply chain resiliency while winning the tech war via industrial policy and leveraging the United States’ advantages in oil and gas to achieve energy dominance. Diplomatically, it means making peace with the emerging realist order, setting aside ideological considerations in order to forge the pragmatic alliances that are needed to maintain the balance of power in East Asia, even if that means less attention is devoted to Europe and the Middle East. In its extensive treatment of the economic “sinews of power” (p. 111), No Peer Rivals is a welcome departure from the typical grand strategy text, where military considerations usually dominate to the exclusion of all else.

Overall, Popescu has made a major contribution to the American grand strategy debate. He rigorously draws out from offensive realism a comprehensive approach for ensuring that China does not out-compete the United States in the military, economic, and diplomatic realms. The book should be widely read in academic and policy circles. All that said, it is fair to question whether the line between offensive realism, Popescu’s theoretical anchor, and his no-peer-rivals approach is as straight as the book implies. Recall that John Mearsheimer’s The Tragedy of Great Power Politics (2001), the seminal statement of offensive realism, leans heavily on the stopping power of water, or the way that large bodies of water inhibit the ability of armies to take and hold territory in the face of committed defenders. The stopping power of water creates three complications for Popescu’s argument. First, in the absence of the stopping power of water, the basic logic of offensive realism would point to a grand strategy of global hegemony and not offshore balancing, which Mearsheimer is usually associated with. This is important for Popescu because his no-peer-rivals approach converges with offshore balancing. Arguably, setting the stopping power of water aside, offensive realism points toward a more ambitious strategy than Popescu advocates for, one in which the United States dominates any region from which a rival might plausibly emerge.

Second, and cutting in the other direction, the stopping power of water sheds doubt on exactly how promising China’s prospects for regional hegemony are. Yes, China’s military capabilities are increasingly formidable, and the United States cannot take for granted that it can fend off a Chinese attack on Taiwan at a reasonable cost. However, it is one thing for China to attempt to resolve the Taiwan issue by force. It is quite another for China to overcome the stopping power of water so completely that it dominates the wider region. Japan, for one, will put up stubborn resistance. More likely than Chinese regional hegemony is stalemate, with the stopping power of water giving the advantage to the defender when the stakes are highest. The poorer China’s prospects for regional hegemony, in turn, the less aggressive the United States needs to be in its balancing response. It may be unnecessary, for example, to draw a red line through Taiwan, or to be committed to hobbling China’s economy.

Finally, the stopping power of water should lead even an offensive realist to ask what costs are worth bearing and what risks are worth running to ensure that the United States remains the sole regional hegemon in the international system. If one were to posit that China could overcome the obstacles discussed above and secure regional hegemony in East Asia, how severe of a threat would that pose to the United States? The stopping power of water means that China would not pose a direct threat to the United States. That is, China still would not be able to impose its will on the United States militarily by invading and conquering the homeland. Instead, China would be freer to roam, including into the Western Hemisphere. Yes, this would mean that the United States would be less free to roam itself, but is such an outcome really so dire that the United States should be willing to fight a major war, even a nuclear one, on China’s doorstep?

In sum, offensive realism can certainly support the no-peer-rivals approach that Popescu prefers. However, it could also support a more or less ambitious grand strategy, depending on how seriously one takes the stopping power of water. Even those who agree with Popescu that American grand strategy needs a stronger dose of realism in it, given the return of great power competition, have plenty left to argue about.