The notion of Japan developing nuclear weapons has long been considered far-fetched and even taboo, particularly within Japan. Hailed as an example of the success of the international non-proliferation regime, Japan has consistently taken principled stands on non-proliferation and disarmament issues. Domestically, the largely pacifist Japanese public, with lingering memories of the destruction of Hiroshima and Nagasaki by atomic bombs in the closing days of World War II, has widely rejected any nuclear capacity as morally unacceptable. The inclusion of Japan under the U.S. nuclear "umbrella," with regular reiterations from U.S. officials, provides a guarantor to Japanese security. Successive Japanese administrations and commissions have concluded that Japan has little to gain and much to lose in terms of its own security if it pursues a nuclear weapons capability. Today, Japanese officials and experts remain remarkably uniform in their consensus that Japan is unlikely to move toward nuclear status in the short-to-medium term. However, as the security environment has shifted significantly, the topic is no longer toxic and has been broached by several leading politicians. North Korea's test of a nuclear device in 2006 and China's military modernization have altered the strategic dynamics in the region, and any signs of stress in the U.S.-Japan alliance raises questions among some about the robustness of the U.S. security guarantee. An ascendant hawkish, conservative movement—some of whom openly advocate for Japan to develop an independent nuclear arsenal—has gained more traction in Japanese politics, moving from the margins to a more influential position. In addition, previous security-related taboos have been overcome in the past few years: the dispatch of Japanese military equipment and personnel to Iraq and Afghanistan, the elevation of the Japanese Defense Agency to a full-scale ministry, and Japanese co-development of a missile defense system with the United States. All of these factors together increase the still unlikely possibility that Japan will reconsider its position on nuclear weapons. Any reconsideration of Japan's policy of nuclear weapons abstention would have significant implications for U.S. policy in East Asia. Globally, Japan's withdrawal from the Nuclear Non-Proliferation Treaty (NPT) could damage the most durable international non-proliferation regime. Regionally, Japan "going nuclear" could set off a nuclear arms race with China, South Korea, and Taiwan and, in turn, India, and Pakistan may feel compelled to further strengthen their own nuclear weapons capability. Bilaterally, assuming that Japan made the decision without U.S. support, the move could indicate Tokyo's lack of trust in the American commitment to defend Japan. An erosion in the U.S.-Japan alliance could upset the geopolitical balance in East Asia, a shift that could indicate a further strengthening of China's position as an emerging hegemonic power. These ramifications would likely be deeply destabilizing for the security of the Asia Pacific region and beyond. Japan's post-war policy on nuclear weapons and non-proliferation has been to reject officially a military nuclear program. The Japanese Army and Navy each conducted nuclear weapons research during World War II, but neither was successful in gaining enough resources for the endeavor. Despite the fact that by the early 1970s Japan had already acquired the technical, industrial and scientific resources needed to develop its own nuclear weapons, Japanese policy has repeatedly stated its opposition to the development of nuclear weapons. Complicating Japan's anti-nuclear weapons policy has been a post-World War II dependence on the U.S. "nuclear umbrella" and security guarantee. Under the terms of the Mutual Security Assistance Pact signed in 1952 and the 1960 Treaty of Mutual Cooperation and Security, Japan grants the U.S. military basing rights on its territory in return for a U.S. pledge to protect Japan's security. The rejection of nuclear weapons by the Japanese public appears to be overwhelmingly driven by moral, rather than pragmatic, considerations, but Japan's leaders have based their policy of forswearing nuclear weapons on protection by the U.S. nuclear arsenal. The bedrock of domestic law on the subject, the "Atomic Energy Basic Law" of 1955, requires Japan's nuclear activities to be conducted only for peaceful purposes. In 1967, the "Three Non-Nuclear Principles" ( hikaku sangensoku ) were announced by Prime Minister Eisaku Sato, enshrining the policy of not possessing, not producing, and not permitting the introduction of nuclear weapons into Japan. When Japan ratified the Nuclear Non-Proliferation Treaty (NPT) in 1976, it reiterated its three non-nuclear principles, placed itself under the treaty obligation as a non-nuclear weapons state, and pledged not to produce or acquire nuclear weapons. Japan has been a staunch NPT supporter in good standing ever since. Despite multiple reiterations of Japan's non-nuclear status, this orthodoxy has been challenged on several occasions, usually when Japan has felt strategic vulnerability. Probably the most prominent episode occurred in the mid-1960s: China tested a nuclear device for the first time in 1964, and the United States was engaged in the Vietnam War. Prime Minister Eisaku Sato secretly commissioned several academics to produce a study exploring the costs and benefits of Japan's possible nuclearization, the so-called "1968/70 Internal Report." Another secret investigation into Japan's nuclear option was done by the Japan Defense Agency (JDA) in 1995 as Japan assessed its standing in the new post-Cold War environment after the 1994 North Korean nuclear crisis in 1994 and as the international community was considering the indefinite extension of the NPT. Both reports concluded that Japan should continue to rely on the U.S. security guarantee and that development of nuclear weapons would threaten that relationship. Since the end of the Cold War, and particularly in the past decade, developments in the region have increased Japan's sense of vulnerability and caused some in the policy community to rethink Japan's policy of forswearing nuclear weapons development. During the Cold War, the U.S. military presence in Japan represented the Pacific front of containing the Soviets, a reassuring statement of commitment to Japan's security to many Japanese. North Korea's test of a ballistic missile over Japan in August 1998 dispelled the sense of a more secure post-Cold War environment for the archipelago. Moreover, India and Pakistan both conducted underground nuclear weapons tests earlier that year, which to many undermined the success of the international non-proliferation regime and set off fears of a new nuclear arms race. Japan was particularly alarmed at the tests, and instituted a freeze on new loans and grants to the two states. Since then, more provocative behavior from Pyongyang, particularly its 2006 tests of medium-range missiles and a nuclear device, have heightened Japan's fear of potential attacks. The nuclear test prompted prominent officials in the ruling party to call for an open debate on whether to pursue nuclear arms: both then-Foreign Minister (and current Prime Minister) Taro Aso and chairman of the party's policy council called for such a debate before later backing off their comments. In addition to North Korea's activities, a U.S.-India civilian nuclear deal has led to concern among some Japanese non-proliferation experts that the NPT has weakened further. To these experts, the legitimacy and deterrent effect of the global non-proliferation regime underpins Japan's commitment to its own non-nuclear status. While North Korea represents a more immediate danger, many defense experts see China as the more serious and long-term threat to Japan's security. China's rapid military modernization and advancements in weapons systems have compounded Tokyo's concern. Japanese defense papers have pointed to Beijing's apparent progress in short and medium range missiles, its submarine force (some of which have on occasion intruded into Japan's territorial waters), and nuclear force modernization as specific areas of concern. As Chinese military spending continues to accelerate, Japanese defense budgets have stagnated or declined. Although Sino-Japanese relations appear to have stabilized since a period of tension under former Prime Minister Junichiro Koizumi's administration, fundamental distrust and the potential for conflict remains between the Pacific powers. Japan is a country poor in natural resources but with a high level of energy consumption. Since the 1960s, Japan has relied on nuclear power for a significant portion of its energy; nuclear energy currently provides 35% of its electricity. The Japan Atomic Energy Commission's 2005 Framework for Nuclear Energy Policy emphasizes the importance of nuclear power for energy independence and carbon emission reduction. Japan is currently the third-largest user of nuclear energy in the world, with 55 light-water nuclear power reactors (49.58 million kW) operated by 10 electric power companies. The first commercial power reactor began operation in 1966. Two nuclear power plants are under construction, four are in regulatory review, and an additional seven may be built over the next decade. Japan's policy is to achieve a fully independent, or "closed," fuel cycle. The closed fuel cycle promotes the use of mixed-oxide (MOX) fuel in light-water reactors. The set goal is to have 16-18 such reactors by FY2010, and utilities in Japan are now in the process of being licensed for MOX loading and obtaining consent from the local governments. The Japan Atomic Energy Agency (JAEA) was established on October 1, 2005, to integrate Japan's R&D institutes, the Japan Atomic Energy Research Institute and the Japan Nuclear Cycle Development Institute. JAEA carries out R&D work on the full range of fuel cycle activities. Two of the more controversial aspects of Japan's civilian power program are its large stocks of separated plutonium and advanced fuel cycle facilities. Plutonium is a by-product of the uranium fuel used in all nuclear reactors. Plutonium in spent fuel is not weapons-usable.