How do great powers respond to decline? Do they tend to embrace policies that raise the risk of war with rising challengers? These were the core questions that we set out to answer in our book Twilight of the Titans. We focused on these questions because there is a growing consensus among many policymakers and pundits that shifts in relative power are particularly perilous. In an influential 2015 Atlantic Monthly article, for example, the political scientist Graham Allison argued that “war between the United States and China in the decades ahead is not just possible, but much more likely than recognized at the moment. Indeed, judging by the historical record, war is more likely than not” (Allison Reference Allison2015; Reference Allison2017). In 2017, Allison reportedly briefed these findings, which are derived from his accounting of sixteen historical power transitions, to Trump's National Security Council (Crowley Reference Crowley2017). For better or worse, academic arguments about rising and falling powers are helping to shape contemporary Sino-American relations.

Probably for worse, because the marquee finding in our book is that power transition theory is wrong. Ordinal transitions between rising and declining powers tend to be less—rather than more—conflict prone. The main reason why this is the case is because great powers tend to respond to decline not by lashing out against their rising rivals, but by adopting policies of strategic retrenchment. These policies do not always work, and different structural conditions can make it easier or harder for declining powers to use retrenchment to effectively manage decline. Yet to the extent that hawks in the United States are drawing on power transition theory to advocate for “confronting” a rising China or for a strategy of “great power competition,” these policy recommendations are based on flimsy intellectual foundations.

We appreciate the care with which all three of the reviewers have engaged with the arguments and evidence we present in our book. All three seem to accept the basic conclusion: that the impending Sino-American power transition may be turbulent, but that conflict is less likely than not. Yet there are some important areas of dispute. One concerns what the chief source of grand strategy is and how that will affects great power relations. Along with Robert Ross, we tend to rely on structural material factors, while David Kang and Ketian Zhang rely more on domestic and/or non-material factors. The other concerns how conflictual the rise of China will be. Ironically, although we tend to share Ross's analytical focus on systemic factors, we reach a much more optimistic conclusion about the extent to which conditions in the Asia-Pacific are “ripe for rivalry” (Friedberg Reference Friedberg1993).

Let us start with the question of what shapes grand strategy. Our book follows realist theory and argues that actors in international politics, typically states, are primarily interested in their security and survival. This is precisely why states tend to be alarmed by relative decline, because it exposes them to potential harm. Yet beyond this simple and spare assumption, we accept that states can define their security needs in a wide variety of ways, and that culture, history, and domestic politics can matter a great deal in how they do so. Here we are in complete agreement with Kang that one should not “unproblematically assume that all states are the same in the contemporary world.” He is absolutely right to be frustrated that international relations scholars know much more about European than Asian history, a regrettable legacy of imperialism and the Cold War, which is getting better too slowly. We accept that China's conception of its security needs and its role in the Asia-Pacific region will inevitably be shaped by cultural and historical legacies, the same way that Britain's tradition of “splendid isolation” or French conceptions of “grandeur” influenced their grand strategic responses in the cases we explore in our book. Indeed, although our research finds that shifts in relative power are among the most important factors shaping great power grand strategies, we note that the correlation is imperfect. States routinely retrench less than we expect given the depth of their declines, to highlight one notable exception (pp. 53–55).

The question for contemporary US–Chinese relations is the extent to which historical or cultural differences override structural conditions or make it simply impossible to compare cases of rising and declining powers. Here we disagree with Kang that China's experience is not just distinctive, but fundamentally sui generis. It may be true that “the historical East Asian system was hegemonic,” and that as a result, Chinese foreign policy was traditionally oriented more towards monitoring hierarchic relationships rather than managing shifts in the balance of power. Yet British grand strategy was likewise obsessed with questions of imperial management, while the expansion and contraction of contested frontiers were central preoccupations of Russian grand strategy. Similarly, it may well be the case that East Asian history highlights “the dangers of internal challenges rather than external threats.” Yet French policymakers grappled with a rising Germany amidst a contested transition from royalism to republicanism, while domestic unrest and parliamentary protest provided a fatal backdrop for late-tsarist responses to decline. Great powers are inevitably preoccupied with a range of competing concerns—external threats, imperial entanglements, domestic difficulties—all of which are impacted by decline in different ways to varying degrees.

Zhang's core contention is that the making of grand strategy is more complex than we allow for in the book. She notes that there are multiple ways to measure “rising” and “declining,” that grand strategies are sometimes too complex to capture with a single word such as “retrenchment,” and that diplomatic or economic interests can often trump security concerns. We acknowledge all of these points and do our best to defend our choices in the text. We choose one way to measure decline (relative great power share of GDP) and focus on a particular moment of decline (five year windows around an ordinal transition) not because these are the only measures or moments that matter, but because they match those of power transition theorists and are easiest to implement (pp. 5–6, 45–48). We classify and compare grand strategies based on their relative ambition—do they trend towards expansion or retrenchment—not because this is the only or necessarily the best way to think about grand strategy, but because questions of the bearing burdens and managing costs tend to be particularly salient during moments of decline (pp. 6–9, 48–50).

Zhang is certainly correct that there are broader shifts in the character of international politics that may mute our findings. Perhaps globalization has fundamentally transformed the boundaries in which great power competition can take place, thereby rendering the concerns of power transition theorists obsolete (nuclear weapons, international institutions, and the spread of democracy are often cited as having a similar pacifying effect). We try to account for this in our discussion of the “conquest calculus”: when it is harder for states to profit from using force, they will be less likely to choose preventive war in response to decline (pp. 70–71). Yet many of our cases of decline come from nineteenth- and early twentieth-century Europe, when these pacifying forces were relatively weak, and yet great powers still tended to favor retrenchment over war (pp. 40–41, 191–192). Even in familiar and favorable cases, the evidence in favor of power transition theory is thin.

Now that trade networks, international institutions, democracy, and nuclear weapons have remade the global landscape, the implications of our argument tend to be more optimistic. Decline is not destiny, and great powers have considerable latitude to manage power transitions using retrenchment, even in seemingly unfavorable circumstances. We were surprised, therefore, that Ross finds our account “especially pessimistic” about the future of Sino-American relations.

Ross is right that some of the conditions we emphasize may make the United States reluctant to retrench, notably the United States’ unwillingness to surrender preeminence and the apparent absence of regional allies who are willing or able to balance against a rising China. Nevertheless, there are other conditions that appear to favor accommodation and retrenchment: vast distances separate the two biggest powers; the conquest calculus appears to favor the defense; American security commitments are relatively independent, easing worries about falling dominos; and the United States is falling gradually, which leaves time for experimentation and for reforms to bear fruit (pp. 197–198). We concur with Ross's observation about the importance of geography, which can mute incentives to use force and provide opportunities for retrenchment (pp. 39–41). Still, we think these opportunities are not unique to maritime environments. In the 1880s, the vast and dispersed character of Russia's imperial commitments provided it with opportunities to pull back from exposed frontiers while reinforcing key strongpoints. Declining powers often see retrenchment not as a strategy that sacrifices security, but as a means to bolster deterrence and protect vital interests. If so, then the United States was wise to reorient its defense priorities and devote an increasing share of its resources to the Pacific.

As for applications, we would like to consider two: balancing and signaling. Kang builds the case that Asian states are not balancing against China because China is not a threat, is working to reassure its neighbors, and by implication does not much threaten the United States. In contrast, we believe that Kang is excessively optimistic about the intensity of the security dilemma in Asia. At root, balance of power theory proposes that, in a self-help world, great powers generally balance against each other mostly by strengthening their own capabilities; for weaker actors, however, their behaviors are more variable. This is exactly what Kang's Figure 1 shows and exactly what American policymakers fear: China balancing against the United States and most Asian states failing to balance against China. This has led to a rebalancing of US forces to the Asia-Pacific and increasingly fraught relations between the two superpowers. Moreover, and rather than being a sui generis feature of East Asia, this trend is also consistent with historical practice. Our data suggest that rising powers tend to increase defense spending at a faster rate than other great powers, but that they also tend to negotiate more alliance agreements and to get involved in fewer militarized disputes (pp. 64–66). Rising powers often invest in and modernize their militaries, yet also go out of their way to reassure their neighbors. This is a classic balance of power dynamic: great power poles repel each other as weaker states caught in between are generally swept into one orbit or another.

Oddly enough, this allows us to close on an ungloomy note. Zhang has pervasive worries about signaling. What if kindness is mistaken for weakness and US defensive measures signal a lack of resolve? We hope our work can dampen some of these anxieties. Over more than a century, the complexities of power and statecraft have changed. In markedly worse circumstances than those in the contemporary Asia-Pacific, great powers have risen and fallen, made contradictory statements, and pursued contradictory policies, yet across many measures, and controlling for many confounding factors, moments of power transition have tended to be peaceful. For all their manifest imperfections, great powers generally sense power trends accurately, and exchange signals as intended, which has powerfully contributed to peace. While this is no reason for complacency—deterrence can break down, reassurance can fail, historical legacies can cast long shadows—it is no reason for undue alarm either. Contra Allison, the United States and China are not trapped in the same old story of war and change; they remain coauthors of their future.