動態的同盟理論

――分断戦略と結束戦略の相互作用と冷戦初期の米中ソ関係――

抄録

Since the publication of Kenneth Waltz’s Theory of International Politics in 1979, structural realism (neorealism) has occupied the dominant position in the realist paradigm. Criticizing classical realism for its “unscientific” focus on human nature, Waltz posits that the anarchic structure of international system severely constrains states, forcing them to take balancing behavior. While structural realism contributed to making realism more “scientific,” it has generated one drawback; it has turned realist scholars’ attention away from states’ attempts to manipulate external security environments.

This article aims to present an alliance theory, dubbed dynamic theory of alliances, that may overcome the aforementioned drawback. This theory regards the degree of alignments as a product of not only the distribution of capabilities/threats but also a clash between a state’s attempt to divide adversaries (wedge strategy) and an allied state’s effort to maintain/enhance unity with its ally (binding strategy). In other words, an alliance is never in stasis but in a state of dynamic equilibrium, a phenomenon in which an equilibrium situation is achieved when two or more countervailing forces cancel one another. Based on these concepts, this article presents the logic of how states choose different wedge/binding strategies and how interactions between them may influence the formation and breakdown of alliances.

To examine how the theory may explain alliance politics in the real world, the case of the U.S.-China-Soviet relations in the early Cold War period is analyzed. In the late 1940s, Washington aimed to woo Beijing away from the Soviet orbit while Moscow tried to tighten its alignments with Beijing. After the U.S. wedge strategy failed to prevent the formation of the Sino-Soviet alliance in 1950, Washington continued seeking to divide the alliance in the 1950s by using coercion. The case analysis shows that the hypotheses derived from the theory effectively explain the three-way interactions among Moscow, Beijing, and Washington.