国際システムを安定させるものは何か

――核革命論と二極安定論の競合――

抄録

Although the United States and the Soviet Union seriously competed with each other through nuclear arms racing, they never fought each other directly. This is a puzzle because the more severe the conflict is, the higher the incentives become for the conflicting parties to fight. To tackle this issue, I pick up two classical hypotheses explaining the surprising stability of the international system. H1 is the theory of nuclear revolution developed by Robert Jervis. H2 is the stability of bipolar world constructed by Kenneth N. Waltz. The Cuban Missile Crisis is used here to test these hypotheses. This case study is timely because we now know the details of this important political event. As a result of testing these two hypotheses, H1 passed and H2 failed: U.S. decisionmakers, especially John F. Kennedy, first got angry about the Soviet’s sudden installation of nuclear missiles’ sites on Cuba, but he gradually come to favor a quarantine because he was afraid of nuclear retaliation if the U.S. military attacked Cuba. This evidence confirms that H1 is valid. As for H2, this assumes that superpowers do not have to care about alliance politics in the bipolar world because their security is ultimately threated only by the other power, so it should only balance against the other superpower internally. Nevertheless, the United States and the Soviet Union both did worry about how their allies reacted, the US even endangered the missile deal with the Soviets for the sake of its relatively minor ally, Turkey. This evidence of superpower behavior is inconsistent with H2. In sum, the stability of the international system was maintained by the nuclear revolution, at least during the Cold War.