Ansei no Taigoku (suppression of extremists by the Shogunate) (安政の大獄)
The Tairo (chief minister), Naosuke II and roju (member of shogun's council of elders), Akikatsu MANABE signed the Treaty of Amity and Commerce between the United States and Japan without obtaining Imperial sanction and decided to put forward Iemochi TOKUGAWA as successor to the Shogun. Ansei no Taigoku was the oppression of people who were against such policies. More than 100 people, including daimyos (Japanese feudal lords), Kugyo (high court nobles), patriots supporting Sonno Joi (slogan advocating reverence for the Emperor and the expulsion of foreigners) and the Hitotsubashi group (group supporting Yoshinobu from the Hitotsubashi-Tokugawa family), were implicated in Ansei no Taigoku. As a formality, the 13th Shogun, Iesada TOKUGAWA issued a Taimei (Shogunal order) and carried out the punishments described below. Had Iesada not done so, Naosuke II, the only fudai daimyo (a daimyo as a hereditary vassal to the Tokugawa family), would have been unable to punish his superiors, such as the Imperial Court and the Tokugawa family.
In the late Edo period, many foreign ships arrived in Japan. After China lost the Opium War, the awareness of foreign risk rose in Japan and cabinet officials of the Shogunate discussed the issue of coastal defense. The Roju Masahiro ABE carried out the reformation of the shogunate government and entered into the America-Japan Treaty of Amity and Friendship and a treaty between the Russian Empire and the Empire of Japan in 1854.
In 1853, the 12th shogun, Ieyoshi TOKUGAWA died and his fourth son, Iesada TOKUGAWA ascended to be the 13th Shogun, but was in poor health and had no hope to have a son. This have rise the Shogun successor crisis. The successor issue divided the domains into two factions in fierce conflict with each other: One was the Hitotsubashi family supporting Yoshinobu HITOTSUBASHI who had a great reputation for intelligence and was the seventh son of Nariaki TOGUKAWA, the previous lord of Mito Domain; and the other was the conservative Nanki group supporting Yoshitomi TOKUGAWA (later Iemochi TOKUGAWA) who had a close genealogy with the current Shogun and was the lord of the Kishu Domain because of regarding blood line as important.
At this time, Townsend HARRIS, the USA council general, urged the Japanese government to enter into the Treaty of Amity and Commerce. Although the Roju Masayoshi HOTTA tried to break the deadlock by using his authority in the Imperial Court, he could not obtain Imperial sanctions from Emperor Komei since members of the sonjo (royalist) party in Kyoto including Unpin UMEDA prevented it.
In April, 1858, Ii from the Nanki group became Tairo (chief minister). Ii signed the Treaty without Imperial sanction and appointed Iemochi as the heir to the Shogunate. An elderly nobleman of Mito Domain, Nariaki TOKUGAWA had previously retired, but retuned to domain administration and pushed the Mito lord Yoshiatsu TOKUGAWA (the first son of Nariaki), to unite Lords Yoshikatsu TOKUGAWA of Owari Domain and Yoshinaga MATSUDAIRA of Fukui Domain. They realized there was no choice but to sign the Treaty, however as signing it without Imperial sanction would be a great impropriety towards the Imperial family, they made an unscheduled visit to the castle (dates for visiting normally had to be designated) in order to consult with Ii. Ii removed them from their positions as heads of their families and suspended them from office because of their appearance in the castle on an undesignated date.
Although Nariakira SHIMAZU, the lord of Satsuma Domain opposed Ii and planned to march on the capital with 5,000 domain soldiers, he died suddenly in July on that year. After the death of Nariakira, Narioki SHIMAZU who had been forced to retire due to conflict with Nariakira over family issues, seized power. In August, 1859, the government gave a secret Imperial decree to Mito Domain (who had been carrying out covert action against the Imperial Court), and at roughly the same time the chief adviser to the Emperor, Hisataka KUJO who was a government sympathizer was forced to resign his position. As a result, Roju Akikatsu MANABE and Kyoto deputy Tadaaki SAKAI (who was also the lord of Obama Domain of Wakasa Province) went to Kyoto and arrested Mozaemon KONDO and Unpin UMEDA, heralding the start of intense oppression.
Royalists arrested in Kyoto were sent to Edo, questioned in prisons in Denma-cho, Edo and sentenced to severe punishments like Seppuku (suicide by disembowelment) and capital punishment. Even Shogunate cabinet officials Toshiakira KAWAJI and Tadanari IWASE, Kaimei group shogunal retainers of poor lineage, were subject to punishment such as house arrest. It is said that Naosuke II dismissed the very concept of lenient treatment and decided to severely punish any opponents at this time.
After Ii's murder during the Sakuradamongai Incident on March 3, 1860, the oppression ceased.
In accordance with an Imperial order in May, 1862, Yoshinobu HITOTSUBASHI assumed the role of Shogun-kokenshoku (one of three major posts of Edo bakufu), and Shungaku MATSUDAIRA became president of political affairs.
Yoshinobu and Shungaku criticised Naosuke Ii's suppression as an extreme, arbitrary display of power, and ordered the following:
As additional punishment fro the Ii family, a reduction of 100,000 koku (a unit of volume: 1 koku equals 180.39 liters of rice, or 0.278 cubic meters of lumber.)
Punishment for investigators during the oppression
The release of those confined during the oppression
An amnesty to be carried out for the victims who supported Sonno Joi during the Sakuradamongai and Sakashita mongai Incidents as part of the celebrations for Kazunomiya koka (the marriage of the Kazunomiya Imperial princess to an commoner.)
As for the shogun's cabinet officials, the Hitotsubashi family came back into power, the Bunkyu Reform was carried out, Shogun Iemochi married the Imperial princess Kazunomiya, and a reconciliation between the imperial court took place.
Ansei no Taigoku lead to a decrease in general awareness and a shortfall in human resources in the shogunate, plus intensified Sonno activities by the anti-shogunate group, and it is said these were underlying causes in the fall of the government.