As people rushed through the city streets on their way to work, five men stepped onto the packed trains of the Tokyo underground. Although the trains were on separate lines, each had a common destination: Tsukiji Station. This station is situated near the city’s center, so the five trains would have all been filled with sleepy commuters traveling across Japan’s capital during the early morning rush hour. There was nothing suspicious about the five men, or at least nothing that aroused attention from their fellow travelers. However, they had all arrived with the same deadly plan in mind.

At around the same time, each man subtly dropped a plastic bag filled with an unknown liquid onto the floor of their respective trains. They then punctured the bags with the tips of umbrellas as they quickly fled the scene of what was about to become the most terrifying and unprecedented terrorist attack in Japanese history.

By the time each man reached street level, where getaway cars waited for them, the strange fluid had pooled across the carriages’ floors where it was stepped on and splashed by other passengers. As the chemical reacted with the air, it started to give off colorless, odorless fumes that were inhaled by those who remained onboard. People quickly started to sicken, their eyes stinging, some vomiting, and others becoming paralyzed. At the following stations, passengers attempting to escape the carriages ended up spreading the gas as others started to collapse. 

By the end of this horrific event, which took place on March 20, 1995, 13 people, including two subway employees, had been killed by the release of sarin gas on the Tokyo underground, while thousands of others were injured during the subsequent chaos. 

Although it was not known at the time, the lethal nerve agent had been released by the doomsday cult known as Aum Shinrikyo (Supreme Truth), who had been involved in various terrorism incidents and assassinations since the late 1980s. This attack caused widespread panic across Japan and also sparked a new concern among the people of the world: could terrorists and other non-state actors use chemical weapons or other weapons of mass destruction against innocent people in the future? 

Much has changed in the 30 years since Aum’s attack, but what caused this terrifying event to take place – and are chemical weapons as much of a threat now as they were thought to be in the 1990s? 

The Apocalypse was nigh 

To understand how the Tokyo underground attack occurred, we need to explore why Aum Shinrikyo became a millenarian cult, especially as they did not start out as a violent group. 

Founded in the mid-1980s, the first members came together as part of a yoga group led by a partially blind masseur, acupuncturist, and Chinese medicine practitioner called Chizuo Matsumoto. Matsumoto had been deeply interested in New Age religion for a number of years and was particularly fascinated by the idea of extrasensory perception and later divination, mysticism, and importantly, the writings of Nostradamus. 

In 1985, Matsumoto, who eventually changed his name to Asahara Shōkō, started preaching of a coming apocalypse and identified himself and his growing number of followers as the ones who would stop it. However, as time went on, his predictions shifted from his cult members being the ones to avert disaster to them being the only survivors. As Asahara consumed more apocalyptic literature, he decided his followers were to be the ones to initiate Armageddon, rather than to wait to be its victims. It was here that he revealed himself to be The New Christ and a divine messenger. 

This may sound insane to many of us today (or maybe not given the current international situation), but Matsumoto’s charisma and message came at a time when many in Japan felt directionless and lacking in spiritual purpose. His message was particularly attractive to the disillusioned youth, many of whom had backgrounds in science, medicine, and engineering and so were facing pressured futures. 

Within a very short period, the group’s numbers quickly swelled, reaching around 4,000 members by 1989 and about 10,000 in Japan by 1995. In addition to its assets in Japan, Aum also had offices in the United States, Russia, and Germany. 

Although Aum was not initially a violent group, they gradually became more extreme as circumstances turned against them. For instance, in September 1988, a cult member called Terayuki Majima accidentally drowned during a ritual gone wrong. In order to avoid unwanted negative attention at a time when the organization was applying for religious status, Asahara had his body burnt and his bones ground up and secretly scattered across a lake. 

However, Shuji Taguchi, Majima’s best friend, became disillusioned and attempted to leave the cult in 1989. Afraid he would tell the police about the death and its subsequent cover-up, Asahara had Taguchi bound and confined in a container before his inner circle strangled him to death.

Around this time, Asahara decided to make a play for more direct power; he and his most trusted acolytes ran for parliamentary seats during that year’s election. There was extreme resistance to this decision among the general population, and in October 1989, an influential Japanese magazine published the first of seven scathing articles that revealed some of the cult’s darker features. This inspired the families of cult members to form a protest group that hired a civil rights lawyer called Tsutsumi Sakamoto as their legal representative. 

Sakamoto quickly became a significant thorn in Asahara’s side and was subsequently assassinated along with his wife and their one-year-old child. The murder was messy and poorly planned, something that ended up characterizing Aum’s future biological and chemical weapons activities. But despite all this effort to remove Sakamoto’s influence, as well as the millions of dollars spent on the campaign, the election was a complete disaster for Aum Shinrikyo. 

This abject failure spurred Asahara into viewing the wider population as unworthy of salvation and initiated the cult’s transformation into a terrorist organization that would use weapons of mass destruction in its efforts to bring down society. 

Toxic ambitions 

Aum’s interests in chemical and biological weapons represented a strange combination of sophisticated ambition and some dodgy organization. Between 1990 and 1995, the group launched numerous different attacks using various agents, including sarin, VX (an extremely lethal synthetic chemical), phosgene (a chemical that can cause damage to the skin, eyes, nose, throat, and lungs), and hydrogen cyanide, as well as anthrax and botulinum toxin (the main compound used in Botox injections). 

The use of these agents was aimed at both specific targets as well as for dealing with dissident members – although it is not clear, it looks like they killed at least 20 dissidents with VX and may have carried out over 19 other chemical and biological attacks on others.

Despite the scale and complexity of their efforts, Aum made some serious errors when preparing them. For instance, rather than purchasing botulinum toxin through any of its well-connected followers, the group decided to collect samples from soils in the Ishikarigawa Basin, in Hokkaido Prefecture. It is not clear exactly which strains of the bacteria they were able to harvest, but after cultivating it into larger quantities in their laboratories, the cult had only managed to make a very weak product, and lots of it – the strain was so weak that an unfortunate member who slipped into a fermenting tank is said to have come away completely unharmed.  

The organization experienced similar problems with their anthrax specimens. In June 1993, residents in Kameido, Koto-ward, in eastern Tokyo, reported revolting smells issuing from the roof of a property owned by Aum Shinrikyo. Over the course of several weeks, various people complained about the smells as well as the intermittent mist that emanated from two cooling towers on the building. This mist, residents said, seemed to form a gelatinous, oily, gray-black build-up on the side of the building. 

Eventually, the complaints reached the point where Aum was forced to vacate the building on July 2, which they cleared out completely. However, samples of the odd goo were collected and put into storage. And that may have been the end of it if Aum hadn’t carried out the Tokyo underground attack in 1995. 

Once the authorities started investigating the sarin attack, they quickly linked it to the cult, which led to a series of mass arrests and a subsequent investigation into their past activities. During interrogation, Aum members testified that the odors in Kameido had been caused by their attempts to aerosolize anthrax in a liquid medium and to pump it into the air to cause an epidemic, one that would lead to a world war, allowing Asahara to become the ruler of all. 

But as with the botulinum toxin situation, the anthrax strain Aum obtained was not lethal. In fact, it seems they procured a version that was used in veterinary medicine to vaccinate livestock against the disease. As such, it was pretty much harmless and resulted in no serious illnesses among the residents who were exposed to it.

This level of fudging was also apparent in the Tokyo underground attack. Despite the lethal nature of the event, the situation could have been substantially worse if the cult members had a more sophisticated method for releasing the sarin gas. Instead, they relied on the crude approach of bursting bags containing the liquid, which actually limited how many people were exposed to deadly gas.

30 years after the event

To say the Tokyo underground attack had a significant impact on the world would be an understatement. In many ways, it galvanized in the international public’s mind the threat of religiously inspired non-state actors who could target innocent populations with deadly weapons.

It was a time where homegrown terror flocks were about to become very important.

Dr Brett Edwards

As Dr Brett Edwards, a Senior Lecturer at the University of Bath’s Centre for the Study of Violence, told IFLScience, “it was a time where homegrown terror flocks were about to become very important,” especially with Al-Qaeda’s attack on the World Trade Center occurring in 2001.

Despite the various manifestations of terrorist groups across the world over the last three decades, none have matched Aum Shinrikyo in terms of their resourcefulness, widescale ambition, and overall weirdness. 

“They’re a real outlier,” Edwards added. “They were big, well resourced, and they invested time into [preparing for their attacks], and they chose to go down [the weapons of mass destruction] route.”

Across the world, state authorities responded by attempting to strengthen their domestic and international provisions concerning chemical weapons, counterterrorism, and global security. For instance, the attack reinforced the global need to implement the Chemical Weapons Convention (CWC), which opened for signature in 1993, but was still awaiting ratification by several countries (including Japan) in 1995. 

As a result of this reaction, the Organization for the Prohibition of Chemical Weapons (OPCW) officially came into effect in 1997, leading to tighter restrictions on the production, stockpiling, and deployment of chemical weapons. Across the world, governments also strengthened their own domestic anti-terror laws and increased international cooperation to tackle and respond to such incidents while also attempting to pay closer attention to cults or extremist religious groups.

Since that fateful day in March 1995, the world has not seen a terrorist group successfully acquire and use similar weapons. Instead, incidents of chemical weapons use have mostly been at the behest of states themselves. For instance, in 2013, the forces of President Bashar al-Assad, the former president of Syria, used chlorine and sarin gas against rebel forces and civilians during the Syrian Civil War. Similarly, Russia is widely suspected of having used the nerve agent known as Novichok against dissidents such as the ex-spy Sergei Skripal and his daughter Yulia, in 2018, and the Russian opposition leader, Alexei Navalny, in 2020. 

Instead, terrorist groups have increasingly relied on improvised tactics, such as driving vehicles into groups of people or using conventional weapons in more limited events. But does this mean the threat of chemical weapons use by terrorist groups is a thing of the past?  

Poison attacks haven’t been a thing for a long time, but they could be again, and if it happened with a widely available technology, it could be really bad.

Dr Brett Edwards

While it would be easy to assume that future terrorist activities will seek increasingly sophisticated methods, such as synthetically created pathogens, Edwards believes we still need to consider a renewed interest in things like chemical weapons, especially older chemicals that are now easier to make and can be combined with modern methods of delivery. 

“Poison attacks haven’t been a thing for a long time, but they could be again, and if it happened with a widely available technology, it could be really bad,” Edwards explained. “[Y]ou still need specialist work which really [keeps] abreast of the idea that stigma of chemical weapons, the fear of chemical weapons, may perversely incentivize its use [again in the future]. And following on from [the novelty and unusualness of something like the Skripal attacks], these incidents when they happen, require us to have additional forms of preparation in things like dealing with the public”.

“You still need specialism and specialists to be thinking about these issues, because they have certain characteristics, which means you need to integrate additional forms of expertise, knowledge, and history in order to actually understand and respond to them.”

Following the Tokyo underground attack, Asahara and his inner circle responsible for the sarin release were arrested and eventually sentenced to death. They stayed in jail until 2018 when their final appeals were completed and ultimately rejected; their execution soon followed. 

Aum Shinrikyo still exists today but operates under the name Aleph and Hikari no Wa. Although they have tried to distance themselves from the legacy of Asahara’s ambitions, the two groups are still closely monitored in Japan.