In the 1984–1990 window, international cooperation is framed as a function of durable regimes and designed institutions that facilitate coordination in an anarchic world. Research emphasizes formal game-theoretic reasoning, highlighting iterated interactions, reciprocity, and exit options as mechanisms sustaining cooperative outcomes, and it treats security and economic issues as domains where regime-level rules and decentralized enforcement shape behavior. The shift toward regime design, institutionalized norms, and trans-governmental coordination provided a unifying methodological approach that links strategic bargaining with structural design, illustrating how rules and routines can stabilize interaction across competing actors. Historical Significance: This period crystallizes neoliberal institutionalism as a dominant explanatory framework, arguing that regimes can sustain cooperation even after hegemonic influence wanes. By integrating game-theoretic insights with institutional design, the paradigm reframes the gravity of rules and regimes in the world political economy, guiding subsequent analyses of cooperation, regime formation, and policy coordination without centralized enforcement.