Triad Theory and Its Application in International Relations: From Simmel's Social Geometry to Strategic Triangles in Global Politics

International Relations (IR) scholarship has long privileged the dyad as its principal unit of analysis, treating bilateral rivalry, alliance, and bargaining as the fundamental building blocks of world politics. Yet many of the most consequential dynamics of the international system, balancing, bandwagoning, mediation, and the manipulation of coalitions, are irreducibly triadic. This article revisits Georg Simmel's classical sociology of the triad and Theodore Caplow's theory of coalition formation in three-actor systems, arguing that these microsociological frameworks offer significant, underexploited analytical leverage for understanding great-power politics, regional security complexes, and emerging trilateral arrangements. Adapting Simmel's account of mediator, tertius gaudens, and divide-et-impera roles, and Caplow's predictive typology of coalition strength, the article develops a framework for analysing "strategic triangles" in international politics. It applies this framework to four empirical domains: the classic Sino-Soviet-American triangle of the 1970s and 1980s, Randall Schweller's tripolarity model, contemporary triangles such as United States-China-Russia and Russia-India-China, and emergent minilateral arrangements such as AUKUS. The article finds that triad theory illuminates recurring patterns of coalition formation, pivotal bargaining power, and systemic stability that dyadic and purely structural-realist accounts tend to obscure, while also identifying the theory's limitations in accounting for domestic politics, ideational variables, and multipolar complexity. It concludes by proposing avenues for extending triadic analysis to African and Global South regional systems.

Triad Theory, Strategic Triangle, Coalition Formation, International Relations, Georg Simmel, Theodore Caplow, Tripolarity

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