The Tokyo subway sarin attack (Japanese: 地下鉄サリン事件, Hepburn: Chikatetsu sarin jiken; lit. 'subway sarin incident') was a domestic chemical terrorist attack perpetrated on 20 March 1995, in Tokyo, Japan, by members of the Aum Shinrikyo cult. In five coordinated attacks, the perpetrators released sarin, a nerve agent, on three lines of the Tokyo Metro (then Teito Rapid Transit Authority) during rush hour, killing 14 people, severely injuring 50 (some of whom later died), and causing temporary vision problems for nearly 1,000 others. The attack was directed against trains passing through Kasumigaseki and Nagatachō, where the National Diet (Japanese parliament) is headquartered in Tokyo.
The group, led by Shoko Asahara, had already carried out several assassinations and terrorist attacks using sarin, including the Matsumoto sarin attack nine months earlier. They had also produced several other nerve agents, including VX for assassination attempts, and attempted to produce Bacillus anthracis and botulinum toxin for bioterrorism. Asahara had been made aware of a police raid scheduled for 22 March and had planned the Tokyo subway attack in order to hinder police investigations into the cult and perhaps spark the apocalypse the leader of the group had prophesied.
In the raid following the attack, police arrested many senior members of the cult. Police activity continued throughout the summer, and over 200 members were arrested, including Asahara. Thirteen of the senior Aum management, including Asahara himself, were sentenced to death and later executed; many others were given prison sentences up to life. As of 2026 the attack remains the deadliest modern incident defined as terrorism in Japan.
Background
Aum Shinrikyo
Origins
Aum Shinrikyo was founded in 1984 as a yoga and meditation class, initially known as Oumu Shinsen no Kai (オウム神仙の会; "Aum Divine Beings' Society"), by pharmacist Chizuo Matsumoto. The group believed in a doctrine revolving around a syncretic mixture of Indian and Tibetan Buddhism, as well as Christian and Hindu beliefs, especially relating to the Hindu god Shiva. They believed Armageddon to be inevitable in the form of a global war involving the United States and Japan; that non-members were doomed to eternal hell, but could be saved if killed by cult members; and that only members of the cult would survive the apocalypse, and would afterwards build the Kingdom of Shambhala.
In 1987, the group rebranded itself and established a New York branch. In 1988, it opened a headquarters in Fujinomiya. Around this time, the mental health of Matsumoto, now going by the name Shoko Asahara, deteriorated – he developed a health anxiety and expressed suicidal views.
In August 1989, the group was granted official religious corporation status by the Tokyo Metropolitan Government, giving it privileges such as tax breaks and freedom from governmental oversight. This recognition caused dramatic growth, including an increase in net worth from less than 430,000,000 Japanese yen to over ¥100,000,000,000 (approximately US$7,000,000 to US$1,300,000,000 in 2024) over the next six years, and an increase in membership from around 20 members to around 20,000 by 1992.
The drastically increasing popularity of the group saw an increase in violent behavior from its members. In 1988, a member of the cult, Terayuki Majima, accidentally drowned during a ritual. His body was cremated, with the remaining bones ground up and scattered over a nearby lake. In February 1989, Majima's friend, a fellow member of the group, was murdered by members acting under Asahara's orders, after he became disillusioned and tried to leave.
In November 1989, six Aum Shinrikyo members were involved in the murder of Tsutsumi Sakamoto and his family. Sakamoto had been working on a class-action lawsuit against the cult. Asahara had previously advanced the concept of 'poa': a doctrine which stated that people with bad karma were doomed to an eternity in hell, unless they were 'rebirthed' through intervention by 'enlightened people', and that it was acceptable to kill those at risk of bad karma to save them from hell.
Early attempts to seize power
Asahara had experienced delusions of grandeur as early as 1985. In his meditation sessions during this time, he claimed that the god Shiva had been revealed to him, and had appointed him 'Abiraketsu no Mikoto' ('The god of light who leads the armies of the gods'), who was to build the Kingdom of Shambhala, a utopian society made up of those who had developed 'psychic powers'.
In 1990, Asahara announced that the group would run 25 candidates in the election that year to the Japanese Diet, under the banner of Shinrito (真理党, "Truth Party"). Despite showing confidence in their ability to gain seats in the diet, the party received only 1,783 votes. The failure to achieve power legitimately, blamed by Asahara on an external conspiracy propagated by "Freemasons and Jews", caused him to order the cult to produce botulinum and phosgene in order to overthrow the Japanese government. As members became disillusioned with the group, following contact with the outside world made during the election campaign, and defected, an attitude among the remaining members that 'the unenlightened' did not deserve salvation became accepted.
Attempts to stockpile botulinum toxin proved unsuccessful. Seiichi Endo – one of the members tasked with acquiring botulinum toxin – collected soil samples from the Ishikari River, and attempted to produce the toxin using three 10,000-litre (2,600 US gal) capacity fermenters. In total, around 50 batches of 9,000 litres (2,400 US gal) of a crude broth were produced – however, the cult did not attempt to purify the broth, which mostly would have consisted of bacterial cultivation media. One member fell into one of the fermenters and nearly drowned, but otherwise suffered no ill effects.
Despite mouse bioassays run by Tomomasu Nakagawa, another cult member assisting Endo, returning no toxic effects, in April 1990 the crude broth was loaded into three trucks equipped with custom spray devices, which was to be sprayed at two US naval bases, Narita airport, the Diet building, the Imperial Palace, and the headquarters of a rival religious group.
Simultaneously, Asahara announced that the coming apocalyptic war could not save people outside of the cult, and that members should attend a three-day seminar in Ishigakijima in order to seek shelter. The spraying attacks failed to cause any ill effects among the population. 1,270 people attended the seminar, many of them becoming devout monks.
With the intention of building a compound with a phosgene plant, and facilities to manufacture VX and chlorine gas, Aum Shinrikyo used 14 dummy companies to purchase acres of land in Namino, now part of Aso city, and began construction. However, public attitudes towards the cult had become very negative due to suspicions around the cult's illegal activities. These attitudes were exacerbated once it was revealed to the surrounding community that the group had acted illegally. In October 1990, a police investigation resulted in the arrests of several Aum members, causing Asahara to fear a police raid. He ordered the destruction of all biological and chemical weapon stockpiles, and for the cult to focus on legitimate, non-violent strategies only.
Restarting violent activity
After the destruction of the illegal weapon stockpiles, the cult relied on 'mainstream' methods to attract other members – this included frequent television appearances by Asahara, as well as the setting up of the 'Aum Shinrikyo broadcasting' radio station in Russia in April 1992. However, starting in late 1992, Asahara's mental health deteriorated further – he began to complain of hallucinations and paranoia, and he withdrew from public appearances (except on Aum Shinrikyo Broadcasting), claiming society was preventing him from fulfilling his destiny as Christ. The concurrent replacement of the previously predominantly female group of top advisers with a more aggressive male group led to the gradual restarting of the violent campaign to seize power. At some point in 1992, Asahara published Declaring Myself the Christ, in which he identified himself with the "Lamb of God".
He outlined a doomsday prophecy, which included a Third World War, and described a final conflict culminating in a nuclear Armageddon, borrowing the term from the Book of Revelation. His purported mission was to take upon himself the sins of the world, and he claimed he could transfer to his followers spiritual power and take away their sins.
Asahara claimed to be able to see dark conspiracies everywhere promulgated by Jews, Freemasons, the Dutch, the British royal family, and rival Japanese religions.
The president of the Okamura ironworks, an industrial plant facing debt troubles, was a member of the cult who consulted with Asahara about a takeover strategy. In September 1992, Asahara was made president of the ironworks, resulting in 90% of staff being dismissed or leaving due to the 'Aum-ification' of the plant. These workers were replaced with other members of the group. Over the course of 1993, the cult smuggled AK-74 rifles and 5.45x39mm bullets, and began to prototype rifles based on the AK-74 design.
Under the oversight of Endo, the biological weapons division of the cult resumed – this time pursuing botulinum toxin and anthrax, using improved 200-litre (53 US gal) drum fermenters at their Kameido facility.
Again, the group did not attempt to purify the resulting product, which resembled a foul-smelling brown slurry. Further failed attacks on individuals were attempted in 1993 and 1994 using botulinum – first using a homemade sprayer mounted to a car, and then by mixing with juice – but neither had any effects. Five days before the sarin attack on the Tokyo subways, botulinum was dispersed in a failed attack on Kasumigaseki station – a dissident member had replaced the active compound with water, but the cult had failed to acquire an active strain of C. botulinum.
The Aum anthrax program was a failure – despite having access to a sympathiser outside of the group who could acquire anthrax spores, the strain received by the group was a Sterne vaccine strain incapable of causing harm. It was unclear why, despite having this knowledge, the group executed two attacks in 1993 using this vaccine strain – once from the roof of the headquarters building in Kameido, and once from a truck with a custom spraying device, aimed at the Diet building, Imperial Palace, and Tokyo Tower. Both attacks caused no effects other than a foul smell, reported by passers-by.
In the summer of 1993, Endo attempted a different strategy – by desiccating the slurry, the B. anthracis spores could be spread as a powder, rather than through spraying – this was achieved with a crude hot air dryer. Nakagawa has claimed that an attempt was made to spread this powder through the centre of Tokyo, but this, also, had no effects. The total failure of the biological weapons program had, by mid-1993, convinced Asahara to focus on the chemical weapons division under Masami Tsuchiya. While Endo would be promoted within the cult to 'health minister' in 1994 – reflecting his seniority – no further attacks using biological weapons were attempted.
Chemical weapon production
In November 1992, Tsuchiya established a small laboratory in their Kamikuishiki complex. After initial research at Tsukuba University, where he had previously studied chemistry, he suggested to Hideo Murai – a senior Aum advisor who had tasked him with researching chemical weapons in November 1992, out of fear that the cult would soon be attacked with them – that the most cost-effective substance to synthesize would be sarin.
Murai was ordered to produce a small amount. Within a month, the necessary equipment had been ordered and installed, and 10–20 grams (0.35–0.71 oz) of sarin had been produced via synthetic procedures derived from the five-step DHMP process as originally described by IG Farben in 1938, and as used by the Allies after World War II.
After this small quantity had been produced, Murai ordered Tsuchiya to produce about 70 tonnes (150,000 lb). When Tsuchiya protested, noting that this level of scaling was not feasible in a research laboratory, a chemical plant was ordered to be built alongside the biological production facility in the Fujigamine district of Kamikuishiki, to be labeled Satyan-7 ('Truth'). The specialized equipment and substantial chemicals needed to run the facility were purchased using shell companies under Hasegawa Chemical, a chemical company already owned by Aum. At the same time, in September 1993, Asahara and 24 other cult members traveled from Tokyo to Perth, Australia, bringing generators, tools, protective equipment, including gas masks and respirators, and chemicals to make sarin.