Underbalancing is a concept developed most fully by Randall Schweller in his 2004 International Security article "Unanswered Threats: A Neoclassical Realist Theory of Underbalancing" and expanded in his 2006 book Unanswered Threats: Political Constraints on the Balance of Power. It describes situations where a state, despite facing a clear and growing external threat, fails to mobilize sufficient internal resources or form adequate alliances to counter it.
Classical structural realism—particularly Kenneth Waltz's Theory of International Politics (1979)—predicts that states will reliably balance against concentrations of power or threat. Stephen Walt's The Origins of Alliances (1987) refined this into balance-of-threat theory. Yet empirically, states often do not balance, balance too late, or balance with insufficient effort. Schweller argues this anomaly cannot be explained by structure alone and requires looking inside the state.
He identifies four domestic-political variables that drive underbalancing:
- Elite consensus about the nature of the threat
- Elite cohesion (absence of factional infighting)
- Social cohesion within the broader society
- Regime or government vulnerability
When elites disagree about whether a rival is genuinely threatening, when ruling coalitions are fragmented, or when leaders fear that costly mobilization will trigger domestic backlash, balancing behavior is muted or distorted.
Schweller's signature case is interwar France and Britain's response to Nazi Germany in the 1930s, where ideological division, war-weariness, and fragile coalitions produced appeasement rather than vigorous balancing. The concept has since been applied to debates over responses to a rising China, Iran's regional posture, and post-Soviet European defense spending.
Underbalancing is a flagship example of neoclassical realism, which treats systemic pressures as filtered through domestic-level intervening variables. Critics, including some defensive realists, argue the concept risks becoming unfalsifiable if any non-balancing outcome can be attributed to domestic dysfunction.
Example
Schweller cites France's fragmented Third Republic response to German rearmament in the mid-1930s as a paradigmatic case of underbalancing against a rising revisionist power.
Frequently asked questions
Bandwagoning means actively aligning with the threatening power to share in gains or avoid punishment. Underbalancing means failing to balance adequately while not necessarily joining the threat—often through inaction, hedging, or insufficient mobilization.
Keep learning