When, why, and how do states confront threats in international politics? With the possible exception of the causes of war, few issues have received greater scholarly attention. Contemporary international relations (IR) research takes one of two broad tracks. On the one hand, realist scholarship of many stripes proposes that states balance by pooling resources with other actors via alliances, by building up their own armaments, or by doing both. Neoliberal and constructivist accounts, on the other hand, focus on the possibility of building institutions, norms, and conflict resolution mechanisms to inhibit or limit threats from manifesting. Each approach has its proponents, although it is rare for analysts in one camp to fully engage arguments on the other side.

Enter T.V. Paul in his fine Restraining Great Powers: Soft Balancing from Empires to the Global Era. Paul inaugurated a critical debate in the mid-2000s by proposing that the apparent absence of balancing against the United States was really due to the novel forms that balancing took in the contemporary world (see Paul's argument in International Security, 2005; with responses by Robert Pape [2005], Stephen Brooks and William Wohlforth [2005], and Robert Art [2005–6]). As originally construed, international norms against military aggrandizement, robust international institutions, and the preponderant power of the United States meant states were instead primed to “soft balance” the United States: throwing up roadblocks to US foreign policy objectives via ad hoc coalitions and within international institutions.

With the new volume, Paul updates his argument while addressing critics of his original approach. In its revised form, soft balancing expands from an approach to contain a hegemonic power such as the United States in the modern world to a far more common tool of statecraft. As Paul writes, soft balancing means “restraining the power or aggressive policies of a state through international institutions, concerted diplomacy…and economic sanctions in order to make its aggressive actions less legitimate…and hence its strategic goals more difficult to obtain” (p. 20). By this logic, states use soft balancing to variously (1) “impede the target’s ability to profit from bad behavior”; (2) to “increase the marginal cost” for a target in implementing its policies; (3) to “delegitimate” a target state’s efforts; and (4) to signal that more traditional forms of balancing—what Paul calls “hard balancing”—may emerge (p. 23).

Logically, this approach should be more attractive at some times than at others, and Paul identifies “facilitating conditions [that] should exist” (p. 29) for soft balancing to emerge. Most important is that the threat being balanced “should not be existential or even severe”: soft balancing is a tool first and foremost for low-threat environments. Still, it also helps if states (1) put stock in international institutions, legitimacy, and economic interdependence and (2) if hard balancing appears unattractive either because of the absence of great power tensions or power imbalances (pp. 29–33; also p. 168). Collectively, these are fairly restrictive conditions, and one might expect soft balancing to rarely occur. Surveying the history of great power relations since the Napoleonic Wars, however, Paul finds substantial evidence that states—especially the great powers—regularly used sanctions, delegitimation, institutional roadblocks, and the like, to address challengers.

This is an important contribution to IR theory. Most directly, Paul’s work convincingly shows that there is a broader set of tools that states may use to confront opponents than scholars have traditionally looked to and analyzed. Of course, other scholars—including several realists—have flagged such tools (see, e.g., Barry Posen, “European Union Security and Defense Policy: Response to Unipolarity?” Security Studies 15 [2], 2006; Christopher Layne, “The Unipolar Illusion Revisited: The Coming End of the United States' Unipolar Moment,” International Security 31 [2], 2006; Kai He, “Undermining Adversaries: Unipolarity, Threat Perception, and Negative Balancing Strategies after the Cold War,” Security Studies 21 [2], 2012). Paul’s work, however, goes a long way toward systematizing the importance of institutions, economics, and legitimation strategies as mechanisms through which balancing occurs. In the process, it also meaningfully adds to a burgeoning literature that blends realist arguments on the competitive nature of great power politics with neoliberal and constructivist arguments about the changing form and structure of world politics (Stacie Goddard and Daniel Nexon, “The Dynamics of Global Power Politics: A Framework for Analysis,” Journal of Global Security Studies, 1 [1], 2016; Stacie Goddard, When Right Makes Might: Rising Powers and World Order, 2018). Especially for researchers interested in understanding the course and conduct of foreign policy, it is a major and meaningful theoretical intervention. That Paul also successfully surveys such a wide swatch of history and forthrightly acknowledges where his argument succeeds or fails is a leading example of honesty in qualitative social science that others would do well to emulate.

Still, no book is perfect, and Paul’s work has some theoretical and empirical limitations. One issue concerns the underlying logic of soft balancing. As noted, Paul identifies an array of mechanisms by which soft balancing operates and aptly lays them out (pp. 24–30). Still, it remains somewhat nebulous how these steps contribute to “restraining the power or aggressive policies” (i.e., the threat) of another actor; it is unclear how they affect a target’s capabilities or aggressive intentions. Sanctions, for example, might harm the broader economy of a targeted state but do nothing to diminish the threat at hand. Likewise, delegitimation might undercut the political appeal of a target state’s foreign policy but may have little bearing on a target state’s ability to go after other actors. Missing, in short, are clear links between the mechanisms at the heart of soft balancing and the resolution of the security threat posed by the targeted state.

A related problem concerns the project’s framing. From the outset, Paul emphasizes that his work is intended to challenge scholars—primarily realists—who treat balance of power dynamics as synonymous with alliance formation and military arming (p. vii). This is a key insight. Still, the approach introduces an underlying tension. Arming and allying are primarily expected when states confront threats to their vital interests and survival (John Mearsheimer, The Tragedy of Great Power Politics, 2001; Kenneth Waltz, Theory of International Politics, 1979). Soft balancing, however, is expressly a strategy designed to handle limited threats—a circumstance where existing research would not expect traditional balance of power choices to apply; indeed, Paul even acknowledges that traditional balancing remains likely when vital interests are on the line (e.g., chaps. 2 and 8). In presenting soft balancing as a challenge to existing balance of power treatments, Paul thus puts his project in opposition to research that the work actually complements. Far from showing that traditional balancing no longer applies, the work instead highlights that balancing is far more commonplace than previously recognized: there is balancing at all levels, at all times, and in a variety of forms. This does not take away the significance of Paul’s findings—far from it!—but partially obscures what the contribution entails: despite setting out to challenge core tenets of balance of power theory, Paul’s logic points to balance of power theory’s broader salience.

One final issue concerns the empirics. To be clear, Paul’s historical research is impressive, containing insightful syntheses of major historiographic developments and forthrightly acknowledging both where soft balancing does and does not apply: all of this is to the project’s credit. On balance, however, the evidence for soft balancing in the contemporary world—a major motivation and proving ground for the project—may be less clear-cut than allowed.

This issue is clearest in the US-China relationship. Paul writes that from roughly 1991–2010 “the United States …faced a surprising absence of balancing efforts against it” (p. viii, also p. 133); likewise, “China has not been the subject of serious balancing activity” before 2010 (p. 1, also pp. 141–43). Although Paul contends that this seeming puzzle is explained by soft balancing, there is growing evidence that hard balancing was in fact alive and well even before 2010. We now know, for example, that the United States had begun building up militarily and politically against China in the late Clinton years and likely would have done so even more under George W. Bush had the events of September 11 not occurred; likewise, Chinese military policy (i.e., internal arming) seems to have been focused on offsetting US strengths from the 1990s onward (e.g., Nina Silove, “The Pivot before the Pivot: US Strategy to Preserve the Power Balance in Asia,” International Security 40 [4], 2016; M. Taylor Fravel, Active Defense: China's Military Strategy since 1949, 2019). For sure, it is possible that soft balancing occurred alongside more traditional forms of arming and allying in the US-China relationship. Nevertheless, such evidence of hard balancing seems to undercut the salience of soft balancing to international politics under conditions where the argument should readily apply.

Still, these are relatively minor issues. Ultimately, Restraining Great Powers is an important book that needs to be read and engaged by IR scholars. The theory is ambitious, the writing is clear, and the empirical work impressive; in many ways, it is a model for how social science can engage contemporary debates while mobilizing history in support of a broader argument. In extending balancing dynamics to economic affairs and institutions, Paul makes a keystone contribution to a growing wave of research looking to bridge paradigmatic divides in international security studies. Even scholars and policy makers who discount the relevance of soft balancing will find their arguments strengthened and their thinking challenged by Paul’s theory and empirical work. The book is a worthy successor to his International Security article, a significant addition to the IR landscape, and one that analysts of world politics will discuss for a long time to come.