Nuclear
Japan's "Atomic Energy Basic Law" allows only peaceful nuclear activities, and its "Three Non-Nuclear Principles" pledge that Japan will not possess, produce, or permit the introduction of nuclear weapons into the country. Despite Japan's long-standing stance against nuclear weapons, there was an internal debate in the early 1970s about whether Japan should sign the NPT, in part due to concerns about assuring access to nuclear technology to meet national energy needs, and the discriminatory nature of the treaty. Some conservatives were also concerned that closing off the nuclear option might negatively impact future national security needs. In 1968, then Prime Minister Sato commissioned a secret nongovernmental study on the costs and benefits to Japan of developing nuclear weapon capabilities. The existence of this report was leaked to the public in 1994. In the end, the report concluded that nuclearization would negatively affect Japanese security and that the U.S. extended nuclear deterrence is sufficient.

Japan has played an active role in nuclear nonproliferation and disarmament, and has submitted disarmament resolutions to the United Nations General Assembly every year since 1994. Japan ratified the CTBT in 1997 and has been a strong supporter of a Fissile Material Cut-off Treaty (FMCT). However, Japan's security relationship with the United States has tempered Tokyo's emphasis on disarmament. Japan has remained been under the U.S. “nuclear umbrella” even after the end of the Cold War. Despite its increased efforts since the 1990s in the field of nonproliferation and disarmament, Tokyo's two seemingly contradictory nuclear weapon-related policies have made being the champion of nuclear disarmament challenging.

Japan increasingly relies on nuclear power for its electricity needs, and has a highly developed civilian nuclear sector. With almost no indigenous energy sources, Japan’s nuclear energy accounts for over 30 % of the country’s total electricity production, and Japan plans to increase this to 41 % in 2014.  Currently, Japan has 55 nuclear power reactors in operation across the country (the third largest after the United States and France.) Two more new reactors are under construction and 11 are planned to be constructed. Japan has a controversial program for recycling spent nuclear fuel that has produced large quantities of plutonium in the form of metal-oxide nuclear fuel. At the end of 2005, Japan possessed 37.8 metric tons of spent fuel stored at reprocessing plants in Britain and France, along with a domestic stockpile of 5.9 metric tons. All of the nuclear fuel stockpile will ultimately return to Japan for use in domestic nuclear facilities. The original plan called for consumption of the stored fuel by 2010, but due to technical and safety issues, this timetable has been delayed and return of the stored fuel to Japan is proceeding slowly. Some argue this material could provide Japan with a latent nuclear weapons capability. This amount, if further processed for use in nuclear weapons, would be enough for 10,000 warheads.

Japan’s strong commitment to development of a self sufficient plutonium-based nuclear fuel cycle led to the construction of the Rokkasho spent fuel recycling complex in Aomori Prefecture (Northern most prefecture of Japan’s Main Island). This will be the first commercial nuclear fuel reprocessing plant in Japan, and first one in NPT non-nuclear weapon states. Despite strong criticism and oppositions, the reprocessing plant started active testing on March 31, 2006 after many delays and much policy debate. Once the reprocessing plant has started operation, it will separate and stockpile up to 8 megatons of plutonium annually.

Although anti-nuclear sentiment among the Japanese public has far outweighed support for keeping a nuclear option open, several neighboring countries have expressed concerns about possible Japanese nuclear ambitions. Partly in response to these fears, the Japanese government completed an internal study in 1995 that reaffirmed previous conclusions that developing nuclear weapons would damage both Japan’s national security and regional security.

However, recent tension developing in the region, particularly in the Korean peninsula, has led to increased discussions in Japan about the once taboo subject of nuclear weapons development. After North Korea conducted its nuclear weapons test in October 2006, high-ranking Japanese officials made some comments advocating that the debate over developing nuclear weapons should not be prohibited. Despite recent speculation that Japan may reconsider its nuclear options, the deep aversion to nuclear weapons among the Japanese public and Tokyo’s strong commitment to international nonproliferation regimes will likely make any move in this direction difficult.

Biological
Japan had an active biological weapons (BW) program prior to 1945. The focal point was the now infamous Unit 731 based at a laboratory complex in northeastern China during the Japanese occupation. Unit 731 experimented on Chinese civilians and Allied prisoners of war with various biological agents, including plague, cholera, and hemorrhagic fever. In addition to the living body test, the Japanese military used biological weapons against China. Most of the data the Japanese military accumulated during WWII was confiscated by the US military. After World War II, the Japanese government abandoned its BW program. Japan signed the BWC in 1972 and ratified it in 1982. Japan has actively supported negotiation of a protocol to strengthen current BWC provisions. Since the 1995 Aum Shinrikyo's sarin attack and failed attempt to disperse anthrax, Japan has increased its focus on bio-terrorism defenses. Although Japan has a growing biotechnology industry, it is still small in comparison to its chemical industry. As a member of the Australia Group, Japan's biotech industry is subject to a comprehensive set of export controls.
 

Chemical
Japanese scientists began developing chemical weapons (CW) as early as 1917. The Japanese Army used CW after invading China in 1937, conducting an estimated 1,000 to 3,000 attacks. Japan reportedly produced five to seven million munitions containing agents such as phosgene, mustard, lewisite, hydrogen cyanide, and diphenyl cyanarsine. Although Japanese forces used many of these munitions between 1937 and 1945, a considerable amount was abandoned when Japanese forces retreated. After World War II, Japan pledged to not produce CW and participated in the negotiations for the CWC, which Japan signed in 1993 and ratified in 1995. Japan's CWC obligations include the responsibility for the disposal of abandoned CW (ACW) in China. Between 300,000 to 400,000 munitions remain in China's Jilin Province. The deadline for completion of the clean-up is 2007, but Tokyo and Beijing have requested a five-year extension from the OPCW. Japan's chemical industry is the world's second largest, with about 16 percent of global chemical production. As a member of the Australia Group, Japan has developed comprehensive and well-enforced export controls on chemical weapons precursors and dual-use items. Since the 1995 Aum Shinrikyo sarin attack, Japanese spending on CW defense has increased.
 

Missile
Japan does not have a ballistic missile development program, but its space program includes a number of technologies that could potentially be adapted to long-range missiles. The solid-fueled M-5 rocket system, first launched in 1995, includes technologies that could be adapted to develop intercontinental ballistic missile (ICBM) capabilities roughly similar to those of the U.S. MX Peacekeeper missile. Japan's two-stage H-2 rocket is capable of placing a two-ton payload into orbit, but the H-2 is not optimal for ballistic missile applications due to its reliance on cryogenic liquid hydrogen and oxygen fuel. Japan lacks sophisticated command and control systems, as well as some guidance and warhead technology that would be necessary to develop operational missiles. Japan is an active member of the MTCR and was involved in drafting the International Code of Conduct Against Ballistic Missile Proliferation (ICOC). Recently, Japan has become more assertive in the field of space activities. On June 20, 2007, Japan’s ruling coalition submitted the “Basic Space Bill” to the House of Representatives. The bill includes provisions to enable the military use of space for defensive purposes.

Japan has partnered with the United States to research, develop and deploy ballistic missile defense systems.(BMD). After the 1998 Taepodong-1 missile test by North Korea, Japan decided to undertake research and development of missile defense systems in cooperation with the United States. In December 2003, the Japanese government decided to introduce the multi-layered defense system. As regional security concerns over North Korea’s nuclear weapons and missile program intensified, Japan decided to accelerate missile defense deployment. The United States deployed a ground-based Patriot Advanced Capability (PAC)-3 unit at Kadena Air base in Okinawa in October 2006 and Japan deployed its first PAC-3 at Iruma Air Base in Saitama prefecture in March 2007. Its second PAC-3 interceptor system was deployed in November 2007 at the Air Self-Defense Force Narashino base in Chiba Prefecture, near Tokyo.  Nine more installments are scheduled by March 2011. Japan also accelerates its deployment of the sea-based Standard Missile (SM)-3 by expediting modifications on four Aegis ships to be equipped with the SM-3 between 2007 and early 2011. 

Other resources

Japan Takes steps to integrate with U.S. Ballistic Missile defense Japan's Disarmament and Non-Proliferation Policy (Third Edition, March 2006)