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Documents reveal past Japan-U.S. nuclear discussion (Part 5): Where is the shared vision of the alliance today?

By Naotaka Fujita


In this series of articles, I have examined, together with several scholars, classified Ministry of Foreign Affairs (MOFA) documents from the 1960s that were released this year. The 1960s were a time when China’s nuclear development caused turmoil for Japan and the U.S. The documents from half a century ago have taught us many things. The final installment in the series will feature Keio University professor Ken Jimbo, a specialist in Japan’s alliance with the U.S. in the 1960’s who actively offers his views on East Asia’s security.


There has always been an “alliance dilemma” with the Japan-U.S. alliance, under which Japan depends upon the U.S.’s nuclear umbrella: Anxiety over whether Japan will be abandoned. Jimbo says that he was “impressed” to learn that careful discussions were held at the time to prevent such an occurrence.


One example of these discussions is a document titled “Asia’s Threat Today” (by MOFA’s international information department), which was drawn up before the Security Sub-Committee (SSC) meetings of top level Japanese and U.S. officials began in 1967. This document analyzed the threat of China possessing nuclear weapons, and its contents were reflected in the remarks made during the negotiations. At the time, China did not have normalized diplomatic relations with either Japan or the U.S.


The document states:


  • If China’s missile development is limited to intermediate-range missiles that are not capable of reaching the U.S., retaliation by the U.S. has credibility since the U.S. has long-range missiles. Therefore, China’s nuclear threat against Japan has no credibility
  • If China possesses long-range missiles but the U.S. does not build anti-ballistic missiles, the credibility of U.S. retaliation will be diminished and China’s nuclear threat against Japan will have credibility.


Jimbo notes that it is “very meaningful” that this document conveys to the U.S. “an ally’s understanding that the requirements for the function of the nuclear umbrella would change as China’s military capabilities were improved.” Jimbo says that these points can further lead to “discussions on the idea that ‘if the U.S. greatly enhances its missile defense, then China will try to contain the U.S. not by using long-range missiles but by threatening Japan.’” Jimbo says he tells U.S. scholars that this idea is still valid today.


Jimbo also notes that during the U.S.’s discussions of anti-ballistic missiles at the SSC meeting, the U.S. side said the contents of the discussions were the same as those of the “president’s briefings and explanations given at the North Atlantic Treaty Organization (NATO).” Jimbo says that “the U.S. called for Japan’s understanding on U.S. nuclear strategy at the same level as European allies” and says he was surprised that Japan-U.S. negotiations that took place fifty years ago were so in-depth.


At the SSC, the U.S. proposed in 1968 that Japan prepare for the possibility of a Chinese nuclear attack with an air defense posture combining the latest U.S.-made weapons such as anti-ballistic missiles. Jimbo views this as an effort to reach a “shared understanding that Japan should prepare for the worst-case scenario on the Asia front, where the Cold War was escalating.”


In his dissertation, Jimbo chose to research the process in which the U.S. created an international order under the Nixon administration through shared understanding with its allies. The U.S. called on its allies to take responsibility for their own defense. The U.S. had Japan, which already had a developed economy, provide economic support to Southeast Asian nations. The U.S. was aiming to achieve stability in Asia after the Vietnam War through division of labor.


Jimbo says that “the source of the U.S.’s power is its leadership to demonstrate to its allies its desired vision and to realize this vision together. This model for the alliance was formulated in the 1960’s and 1970’s. Japan has at times felt some tension, but has become accustomed to this model over the years.”


The current Trump administration espouses an America First policy. The administration places priority on “deals” to pursue its own short-term benefits rather than a mid- to long-term vision with its allies. Jimbo says that it is  important to discuss “what would happen if a political decision were made to change the policy on a part of Japan’s defense that the U.S. is solely responsible for, such as the nuclear umbrella ?”

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