Japan is the only country on earth to have had nuclear weapons used against its people, and the population has historically been highly opposed to the use of nuclear energy for military purposes. In 1967, Prime Minister Eisaku Sato made this opposition official when he declared Japan’s Three Non-nuclear Principles: The country would not produce, possess or allow nuclear weapons on Japanese territory. Japan has maintained a sophisticated civilian nuclear infrastructure, and despite its Nuclear Non-Proliferation Treaty (NPT) membership, it is believed that Japan could build nuclear weapons quickly if it chose to do so.
But it is highly unlikely that Japan will seek its own nuclear arsenal in the foreseeable future. Beyond public opposition to nuclear weapons, which has only increased since the Fukushima disaster, Japan does not yet have reason to believe it needs an independent deterrent. The U.S.-Japan military alliance has strengthened with the passing decades and has proven highly responsive to Japanese security concerns. On several occasions, Japan has reassessed its non-nuclear status, and has always concluded that the U.S. security guarantee is a superior option. There is little reason to believe that Japan will rethink its commitment to that alliance now.
The U.S. extended a security guarantee to Japan with the end of its postwar occupation of the country in 1952. Eight years later, the pact was revised to eliminate U.S. policing powers. That revision made the U.S.-Japan guarantee similar to the treaties that existed with the Republic of Korea (ROK) or with Australia. Article 9 of Japan’s “peace” constitution, however, has traditionally been interpreted as prohibiting collective self defense. Japan can receive military aid from the U.S., but cannot provide defense assistance to an ally. At its founding, then, the U.S.-Japan alliance had the qualities of a unilateral guarantee, as opposed to a cooperative mutual defense pact. Since 1960, the U.S.-Japan relationship has seen at least two periods of security uncertainty—one in the late 1960s-early 1970s, and one in the mid-1990s. It has come out of each of these stronger than before, with alliance cooperation greatly strengthened.
Following the first Chinese nuclear test in 1964, several high-level Japanese officials suggested the country might seek its own nuclear arsenal. The mid-late 1960s were a tenuous time in the US-Japan alliance: Japan requested that Okinawa be returned to Japan, Richard Nixon announced the Guam Doctrine, and the Nuclear Nonproliferation Treaty opened for signature in 1968.
The most sensitive issue in U.S.-Japanese alliance relations during this period was the reversion of Okinawa to Japanese control. The U.S.-Japan Security Treaty was up for extension or abrogation in 1970, and American officials were concerned that a row over Okinawa could bring the alliance down. The U.S. had administered the island for two decades, and it had come to rely on it as a key storage facility for tactical nuclear weapons. Beyond its strategic role in the U.S.’s defense of Japan, Okinawa was also part of war planning for contingencies in South Korea, Taiwan, and Vietnam. Analysis by the Joint Chiefs of Staff concluded that the return of Okinawa might be an administrative inconvenience, but that the health of the U.S.-Japan alliance made it worthwhile. The return of the island became official in 1972, and the alliance treaty was renewed. But Nixon’s Guam Doctrine, declaring a drawdown of U.S. troops in Asia, still gave the Japanese cause for concern. If the U.S. was unwilling to maintain a robust conventional presence in the region, should the Japanese sign the NPT and firmly commit to non-nuclear status?
Despite his Three Non-Nuclear Principles, Prime Minister Sato authorized several high-level studies probing Japan’s nuclear options. The U.S. also reevaluated the utility of its nuclear umbrella guarantee to Japan, concerned that its partner was unwilling to contribute more to its own defense. In the end, both partners independently concluded that the alliance was a far better option than any other. The allies formed a new bilateral committee for defense cooperation, and drew up new guidelines to govern their military relationship, and Japan acceded to the NPT. This period of flux ended with the first-ever codification of U.S.-Japan military procedures for peace and wartime—“The 1978 Guidelines on Japan-U.S. Cooperation.”
The 1990-1996 period was, likewise, a time of great alliance uncertainty as the end of the Cold War called into question the utility of the United States’ military presence in East Asia. The Bush Administration’s 1990 “Strategic Framework for the Asian Pacific Rim” recommended a three-phased withdrawal of forward deployed forces in the region. China’s imminent rise had also become apparent to many analysts in Japan, and North Korea’s nuclear ambitions came to the fore in 1993. With the permanent extension of the NPT looming in 1995, the Japanese once again reevaluated their security options.
A 1994 study by the Japanese Defense Agency took stock of the US security guarantee and assessed Japan’s nuclear options. The report concluded that Japanese nuclear acquisition would unravel the NPT, destroy the U.S.-Japan Alliance and be extremely costly. It argued that even if North Korea acquired nuclear weapons, Japan should still foreswear them, as the U.S. umbrella was far more valuable than the defense they could guarantee domestically. The conclusions recommend strengthening the bilateral alliance, rather than breaking away from it. The U.S. also took stock of the alliance through the Nye initiative, and concluded that its partnership with Japan was crucial. It abandoned the three-phased force reduction plan, re-committing to the region. President Clinton and Prime Minister Ryutaro Hashimoto called for a defense cooperation review in 1996.
The allies drafted new military guidelines in 1997. These resulted in more information sharing among the parties, and coordination in peacekeeping operations and humanitarian affairs. They also provide for bilateral defense planning during peacetime, and encouraged bilateral military training and exercises. An upgraded Two-Plus-Two Security Consultative Committee now includes the U.S. Secretaries of State and Defense and their Japanese counterparts, and issues regular Defense Policy Reviews. The U.S. and Japan began to develop missile defenses cooperatively in 1998. In short, the flux of the 1990s once again left the U.S.-Japan alliance in far stronger shape than it had been before.
In the decades since 1951, the U.S.-Japan alliance has evolved from a unilateral security guarantee by a former occupier into a true military and political partnership, crucial to the security of East Asia. New regional security challenges have been the catalysts for this process. This security umbrella is not only strong, but has proven to be extremely flexible and responsive to the evolving needs and concerns of both partners.
Given the complex nuclear history of East Asia, it is not entirely surprising that the addition of the phrase “national security” to the Basic Atomic Energy Law caused some alarm both inside and outside Japan. But observers should not assume that this amendment means that the country is seriously rethinking its nuclear future. China’s rise and North Korea’s nuclear status will mean that Japan faces new military and political challenges in the coming years and decades. But the U.S.-Japan alliance has proven itself to be a dynamic one, and chances are good this umbrella can weather these too.
Mira Rapp-Hooper is a doctoral candidate in political science at Columbia University where she is completing a dissertation on extended deterrence and alliance politics.