Sakuradamon incident (1860)

The Sakuradamon Incident (桜田門外の変, Sakuradamon-gai no Hen^?, or 桜田門の変 Sakuradamon no Hen) was the assassination of Japanese Chief Minister (Tairō) Ii Naosuke (1815–1860) on 24 March 1860 by rōnin samurai of the Mito Domain, outside the Sakurada Gate of Edo Castle.

Ii Naosuke, a leading figure of the Bakumatsu period and a proponent of the reopening of Japan after more than 200 years of Seclusion, was widely criticized for signing the 1858 Treaty of Amity and Commerce with the United States Consul Townsend Harris and, soon afterwards, similar treaties with other Western countries. From 1859, the ports of Nagasaki, Hakodate and Yokohama became open to foreign traders as a consequence of the Treaties.

Ii Naosuke was also criticized for reinforcing the authority of the Shogunate against regional Daimyos through the Ansei Purge. Naosuke made strong enemies in the dispute for the succession of Shogun Tokugawa Iesada, and because he forced retirement on his opponents, specifically the retainers of Mito, Hizen, Owari, Tosa, Satsuma and Uwajima.

...
Wikipedia