Japan and weapons of mass destruction

Beginning in the mid-1930s, the nation of Japan conducted numerous attempts to acquire and develop weapons of mass destruction. The 1943 Battle of Changde saw Japanese use of both bioweapons and chemical weapons, and the Japanese conducted a serious, though futile, nuclear weapon program. After the end of World War II the nation was forced to cease all production and abandoned their experiments.

Since World War II, Japan has become a nuclear-capable state, said to a be a "screwdrivers turn" away from nuclear weapons, having the capacity, the know-how, and the materials to make a nuclear bomb. Japan has consistently eschewed any desire to have nuclear weapons, and no mainstream Japanese party has ever advocated acquisition of nuclear weapons or any weapons of mass destruction. Such weapons are forbidden by the Japanese constitution.

Bioweapons
During the Sino-Japanese War (1937-1945) and World War II, Unit 731 and other Special Research Units of the Imperial Japanese Army conducted human experimentation on thousands, mostly Chinese, Russian, American and other nationalities as well as some Japanese criminals from the Japanese mainlands. In military campaigns, the Japanese army used biological weapons on Chinese soldiers and civilians.

This employment was largely viewed as ineffective, due to inefficient delivery systems. However, information has surfaced in the last decade, which alleges a more active Japanese usage. For example, firsthand accounts testify the Japanese infected civilians through the distribution of plague-infested foodstuffs, such as dumplings and vegetables.

There are also reports of contaminated water supplies. Such estimates report over 580,000 victims, largely due to plague and cholera outbreaks. In addition, repeated seasonal outbreaks after the conclusion of the war bring the death toll much higher.

During Changde chemical weapon attack attacks, the Japanese also employed biological warfare by intentionally spreading cholera, dysentery, typhoid, bubonic plague, and anthrax. Other battles include: Kaimingye germ weapon attack.

Chemical weapons
The Japanese used mustard gas and the blister agent Lewisite, against Chinese troops and guerillas in China, amongst others during the Changde chemical weapon attack.

Experiments involving chemical weapons were conducted on live prisoners (Unit 516). As of 2005, 60 years after the end of the war, canisters that were abandoned by Japan in their hasty retreat are still being dug up in construction sites, causing injuries and allegedly even deaths.

In December 1993, Japan signed the Chemical Weapons Convention, ratified it in 1995 and was thus a state party upon entering into force in 1997.

However, JSDF possess chemical weapons facilities and some samples for protection which it said JGSDF Central NBC protection Troop.

In 1995, JGSDF admitted possession of sarin for samples.

Nuclear weapons
A Japanese program to develop nuclear weapons was conducted during World War II. Like the German nuclear weapons program, it suffered from an array of problems, and was ultimately unable to progress beyond the laboratory stage before the atomic bombings of Hiroshima and Nagasaki and the Japanese surrender in August 1945.

The postwar Constitution forbids the establishment of offensive military forces, and in 1967 it adopted the Three Non-Nuclear Principles, ruling out the production, possession, or introduction of nuclear weapons.

While there are currently no known plans in Japan to produce nuclear weapons, it has been argued that Japan has the technology, raw materials, and the capital to produce nuclear weapons within one year if necessary, and some analysts consider it a de facto nuclear state for this reason. For this reason Japan is often said to be a "screwdriver's turn" away from possessing nuclear weapons.

Delivery systems
Solid fuel rockets are the design of choice for military applications as they can remain in storage for long periods, and then reliably launch at short notice.

Lawmakers made national security arguments for keeping Japan's solid-fuel rocket technology alive after ISAS was merged into the Japan Aerospace Exploration Agency, which also has the H-IIA liquid-fuelled rocket, in 2003. The ISAS director of external affairs, Yasunori Matogawa, said, "It seems the hard-line national security proponents in parliament are increasing their influence, and they aren't getting much criticism…I think we’re moving into a very dangerous period. When you consider the current environment and the threat from North Korea, it’s scary."

Toshiyuki Shikata, a government adviser and former lieutenant general, indicated that part of the rationale for the fifth M-V Hayabusa mission was that the reentry and landing of its return capsule demonstrated "that Japan's ballistic missile capability is credible."

At a technical level the M-V design could be weaponised quickly (as an Intercontinental ballistic missile) although this would be politically unlikely.