脅威認識と拡大核抑止の信頼性 : 日本と西独のNPT加盟への葛藤

Since the Sputnik shock, doubts about the reliability of extended nuclear deterrence, whether Defender would risk their own security to assist Protégé, have been debated. Previous studies have emphasized that mutual trust between the Defender and Protégé is essential to reliability. However, extended nuclear deterrence is more like a three-party game. Both Defender and Protégé are influenced by their perceptions of Challenger's objectives, and those perceptions shape their own actions. Therefore, the author examines the reliability of extended nuclear deterrence from the perspective of threat perception. This article uses the examples of Japan and West Germany, both of which are U.S. allies that have renounced nuclear possession. By focusing on these two cases, the author analyzes their threat perceptions during the period when the two nations decided to join the Nuclear Non-proliferation Treaty and tries to measure how their threat perceptions affect their decisions on nuclear weapons. The conclusion drawn is that there is a positive correlation between the threat perception of Protégé and the reliability of extended nuclear deterrence, while there is a negative correlation between the differences in threat perception between Defender and Protégé and the reliability of extended nuclear deterrence.