Tokugawa Iesada
The death of Shōgun Tokugawa Iesada in 1858 led to a power struggle over the succession of the shōgun. At the same time, various factions were debating the foreign policy issue, and the stability of the Tokugawa shogunate was compromised. There were two potential shōgun, and one of them was Hitotsubashi Keiki, Nariaki's son. To solve the problem, the "fudai daimyōs" put Ii Naosuke in charge as great councilor ("Tairō") of the shogunate. Ii decided to punish supporters of Nariaki in order to re-establish the power of the shogunate. While Ii was temporarily successful in maintaining order, his purge of Nariaki supporters in the domains and the court, the Ansei Purge, drove young Mito radicals to assassinate him in 1860 (Sakuradamon Incident). In response to the assassination, the shogunate pacified the radicals by changing shogunal policies in the Bunkyū Reforms and naming Hitotsubashi Keiki as guardian of the shōgun.