North Korea’s ballistic missile tests in July 2006 shone a spotlight on security issues in East Asia. The media paid much attention to political challenges facing the U.S.-ROK alliance. Another top story was Japan’s evolving defense posture and international security role. In October 2006, North Korea tested a nuclear device just as the new Japanese prime minister arrived for an important visit to Seoul. What was supposed to be a summit for moving past historical antagonisms was instead a precursor of contrasting Japanese and South Korean approaches toward Pyongyang.

In addition to the main question of how the world should deal with North Korea, commentators pondered what China’s role would be, and what implications North Korea’s nuclear test would have for the global nonproliferation regime and potential proliferators like Iran. To avoid the possibility of nuclear dominoes in East Asia, security specialists pointed to an urgent need for the United States to reassure its allies South Korea and Japan about the credibility of the U.S. nuclear umbrella.

In the midst of all these developments, virtually no public debate was devoted to how South Korea and Japan need to reassure each other. Theoretical work clearly links changing military capabilities and shifting security environments with problems of reassurance. Studies focused on East Asian security have highlighted the need for reassurance to avoid conflict in the region. While official statements out of Seoul express concern for Tokyo’s security policies, little consideration is given to how South Korean foreign policy is factoring into Japanese strategic calculations. This paper seeks to fill that gap by addressing the question: If Seoul has reservations about the direction of Japanese

security policy, what can South Korea do about it?