Unanswered Threats: Political Constraints on the Balance of Power by Randall Schweller (review)

Why did Great Britain and France not balance effectively against a rising Nazi Germany? Why have states perennially failed to counter the United States, first as it emerged as a great power and then as it became increasingly dominant? These difficult but important puzzles are among several addressed by Randall Schweller’s insightful analysis in Unanswered Threats: Political Constraints on the Balance of Power. Schweller’s theory of “underbalancing” has made a two-fold contribution to international relations theory in the years since it appeared. It provides a neoclassical realist model to explain why states do not adequately respond to systemic pressures; and it has opened new windows of inquiry within balance-of-power theory, which has traditionally ignored the domestic politics dimension. For policymakers and for the general public, Unanswered Threats offers a fascinating account of the nature and causes of crucial political mistakes in world history and raises important questions about why states fail to act as they should if they are to survive and thrive in the international system.

Kenneth Waltz’s neorealist view of the balance of power is that of a theory of systemic outcomes. Schweller complements this approach with a theory of foreign policy that can explain state strategies and variations in national responses to similar systemic pressures. Thus, Unanswered Threats examines how the internal structures of states affect policy responses. Schweller drops the neorealist assumption that all states have the same extractive capacity and instead explores the question of why some states are better than others at recognizing external threats and at mobilizing resources effectively to meet them.

The neoclassical realist answer that Schweller proposes is that appropriate balancing depends on the willingness and ability of political elites to mobilize support and implement policy changes. The closer that the policymaking process and state-society relations are to the image of a unitary actor, the more accurate neorealist predictions will be. Schweller’s argument is that states often fail to balance properly because they rarely look anything like the billiard balls beloved by structural realists. Thus, Unanswered Threats proposes that four factors at the domestic-political level of analysis inhibit effective balancing: elite consensus, elite cohesion, social cohesion, and regime vulnerability. According to Schweller, negative scores on these four variables form antecedent conditions that are jointly sufficient for underbalancing to occur.

Schweller suggests that political elites have to agree about the existence and nature of the threat, the type of strategic adjustment required, and the risks and costs associated with such policies. If policymaking circles are fragmented and marked by bitter struggles for power—and if political elites disagree over the allocation of resources, the ranking of threats, and the preferences for alliances—then the state is unlikely to be able to act according to the realist logic of balancing. Similarly, regimes whose leaders are likely to be removed from office display both a lower ability and a lower willingness to mobilize resources and balance. Weak regimes lack the legitimacy and political capacity to extract the resources necessary for balancing, and they might also be hesitant to mobilize military resources out of fear that it would turn mass armies against them.

Schweller tests his theory of underbalancing using the cases of Britain and France between the two world wars; a longitudinal study of France from 1887 to 1914; and the case of the Triple Alliance War of 1864–1870. Great Britain in the interwar period exemplifies what Schweller identifies as underbalancing through wishful thinking. Because of social unrest, strong labor support for social legislation, and extensive demands for social programs among the British population, military spending was politically infeasible, and British elites preferred domestic sociopolitical stability over rearmament. France before the Second World War is an illustration of a polarized democracy, deeply divided across ideological and class lines, with a weak and unstable government that adopted incoherent half measures and contradictory policies in response to the German threat.

The longitudinal study of France explores...