Literally "Relaxed Governance," Ansei was the 239th nengo, or Imperial reign-name era, in the Japanese calendar, but it was anything but relaxed. Corresponding to the Gregorian years of 1854-1860, it was in fact one of the most tumultuous and momentous times in Japanese history.
Coming on the heels of "Opening of Japan" by Commodore Perry in 1854 with the signing of the Treaty of Kanagawa, the Ansei era witnessed Japan opened to trade and interaction with the West for the first time in over 250 years. The prestige of the Tokugawa shogunate was greatly weakened by the arrival of the foreigners as it was bullied into signing increasingly unequal treaties, culminating in the Harris Treaty of 1858 and the rest of the copycat "Ansei Pacts" signed later that year with the other Great Powers.
The shogunate's eroding power was further undermined by several other unfortunate events. The Great Ansei Earthquake struck in 1855, killing more than 10,000 people and destroying much of Edo, and was seen by many as an ill-omen or a punishment by the gods for the ending of national seclusion. Another headache for the reeling shogunate was the "sonno joi" revolutionaries that sprouted up all around the country, rallying under their slogan of "revere the emperor, expel the barbarians." To make matters even worse, the reigning shogun was the sickly Tokugawa Iesada, who perpetually hovered on the verge of death, precipitating a succession dispute.
In mid-1858, the theretofore pliant Imperial court at Kyoto, emboldened by the sonno joi extremists, surprised everyone by directly challenging the shogunate and refusing to authorize the Harris Treaty. The shogunate responded by elevating the ruthless Ii Naosuke to the position of Grand Chancellor, and Naosuke took decisive action by conducting the Ansei Purge, cleansing the government of all sonno joi and court sympathizers. He then had the Harris Treaty signed on his own authority and outmaneuvered several powerful daimyo to force through the shogunate's choice to succeed Iesada.
Naosuke thus briefly arrested the decline of the shogunate's power, but in 1860, as the Ansei period drew to a close, he was assassinated by agents of Mito domain, a sonno joi hotbed, just outside the gates of Edo Castle. The shogunate would linger on for seven more years, but with its last capable administrator lying dead on the Edo streets, it was the beginning of the end of two and a half centuries of rule by the Tokugawa house.
To convert years from the Japanese calendar to the Gregorian calendar or vice versa, consult the following table:
安政元年 Ansei 1 from 11/27/1854
安政2年 Ansei 2 1855
安政3年 Ansei 3 1856
安政4年 Ansei 4 1857
安政5年 Ansei 5 1858
安政6年 Ansei 6 1859
安政7年 Ansei 7 to 3/18/1860
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