Formed in 1987 by Master Asahara Shoko, Aum Shinrikyo was a Japanese cult. Asahara had originally started a yoga school, but after a trip to India in which he met the Dalai Lama and achieved enlightenment in the Himalayas, he changed the name of his school to Aum Shinrikyo (Aum Supreme Truth) and began teaching a combination of Buddhism, Hinduism and Christianity. He gained many followers as he claimed to embody a god, and he secured significant financial donations. The group became increasingly radical, and defectors met violent ends.
By 1995, the group had about 50,000 members, mostly in Russia. By this time, Asahara had begun preparing for war and expected Aum Shinrikyo to take over the government. To deflect police attention away from the group's activities and instigate the violence he prophecized, Asahara orchestrated an attack on the Tokyo subway.
On March 20, 1995, five members of Aum Shinrikyo boarded the subway on different trains. When they arrived at Kasumigaseki, they each placed a package wrapped in newspaper under their seats. They punctured the packages with the tips of their umbrellas and rushed off the train as gas seeped out. They succeeded in killing 12 people and sickening 5,500. Authorities traced the attack to the group and arrested the leadership, largely dismantling the group.