Unipolarity solves interventions by providing the US with the freedom of action to avoid ill-advised fights. BUT retrenchment causes prolif of proxy conflicts and adventurism.

Systemic Dimensions: The Varying Prevalence of Competitive Intervention

The framework articulated above not only provides a comprehensive account of the duration effects of competitive intervention on civil wars—it also highlights a candidate explanation for the recent decline in the prevalence of intrastate conflict. Insofar as state decisions to aid combatants are consistent with competitive state policy-making, temporal variation in geopolitical competition between states should affect trends in the prevalence of competitive intervention. Variation in the prevalence of competitive intervention should in turn affect temporal trends in the prevalence of internal conflict through the duration effects described above.

Consider the pervasiveness of US-Soviet competition during the Cold War. Bipolarity extended the geographic scope of concern and broadened the range of factors included in the competition between the superpowers. American and Soviet leaders worried that challenges to the existing distribution of power might raise doubts about the credibility of their alliance commitments, thereby encouraging their allies to drift toward neutrality or, worse still, switch sides (Hironaka 2005, 107–11). Because challenges to the status quo were perceived to threaten the relative balance of power and credibility, they were resisted. Yet, because any action by one superpower was perceived as an attempt to gain a geostrategic advantage, it demanded a response. The end result was a proliferation of US-Soviet competitive intervention, wherein the superpowers committed resources to opposing government and rebel forces fighting on the periphery of their spheres of influence.

That many civil wars during the Cold War were superpower proxy wars is a well-rehearsed perspective, but what is missing from existing accounts is an explanation for why superpower sponsorship should be associated with longer conflicts. If foreign civil wars played such a key role in the larger Cold War struggle, why did the superpowers not do what was necessary to help their respective sides win? The theory outlined above provides an answer: challenges to the relative balance of power and credibility necessitated reflexive responses, but the impossible stakes of direct confrontation advised caution. While the superpowers were compelled to intervene, they were simultaneously—and paradoxically—compelled to do so with restraint.

Superpower rivalry also had secondary duration effects. Constrained by the need to both deter and avoid direct confrontation, Washington and Moscow employed indirect strategies for projecting power. Military aid was an integral element of their competition for influence, and accordingly, money and weapons diffused not only to civil wars, but across the international system. This assistance empowered client states, providing a set of Cold War framings and superpower arms that could be used to justify and implement independent foreign policy objectives. Notably, the superpowers struggled to control their clients’ adventurism; by exploiting fears of defection to the opposing bloc, clients found ways to commandeer superpower aid for their own self-interested ends (Krause 1991). The net result was a proliferation of interventions by otherwise weak states in civil wars across the globe.

In the post–Cold War period, by contrast, state clients have a harder time garnering American aid. Regional powers continue to intervene in civil wars, but they can no longer rely on the reflexive support of the USSR when conflicts of interest arise vis-à-vis US policy, nor can they threaten defection to the Soviet-bloc in the face of American sanction. In the unipolar period, the United States has greater choice in which state clients it chooses to support, enjoys greater flexibility to discipline adventurism by weaker powers, and maintains “command of the commons” to restrict flows of economic and military aid around the globe (Posen 2003). Together, these features of the unipolar system constrain foreign adventurism by lesser powers relative to the Cold War period, thereby reducing—though not eliminating—the prevalence of competitive interventions among neighboring states and regional rivals. In this way, the transition from a bipolar to unipolar system not only terminated superpower proxy warfare, but also decreased the rate of competitive intervention by lesser powers.