Mutual Optimism as a Cause of Conflict: Secret Alliances and Conflict Onset

A prominent international-relations theory posits that mutual optimism, due to two sides holding divergent estimates of their relative bargaining power, causes interstate conflict. We develop a theory of mutual optimism in which conflicting bargaining power estimates arise from asymmetric information about which, if any, third parties will join either side in a military dispute. We contend that secret alliances can generate mutual optimism, which increases the probability of conflict. By exploiting secret alliances as a measurable source of private information, we provide the first systematic test of mutual optimism that directly assesses a state's secret capabilities. Optimism exists when a state's secret allies are more numerous or powerful than anticipated by opponents. Our empirical tests—as well as robustness checks—strongly support our theoretical expectation. We conclude that mutual optimism is an empirically, as well as theoretically, important cause of interstate conflict.

一项极具影响力的国际关系理论指出，当双方对彼此的相对议价能力持有差异化评估时，会滋生相互乐观情绪（mutual optimism），最终引发国家间冲突。本文提出一种相互乐观情绪理论框架，认为双方在议价能力评估上的分歧，源于双方在「是否有第三方会在军事争端中加入己方或对立阵营」这一问题上存在信息不对称。本文主张，秘密同盟能够催生相互乐观情绪，进而提升冲突爆发的概率。通过将秘密同盟作为可量化的私人信息来源，本文首次针对相互乐观情绪开展系统性实证检验，且该检验直接对一国的秘密同盟实力进行评估。当一国的秘密同盟在数量或实力上超出对手预期时，便会产生相互乐观情绪。本文的实证检验与稳健性检验均有力验证了本文的理论预期。本文最终得出结论：相互乐观情绪无论是在理论层面还是实证层面，均是引发国家间冲突的重要动因。