Yoshida Shōin
With the increasing number of incursions of foreign ships into Japanese waters in the late 18th and early 19th century, the "sakoku" ("national seclusion") policy came increasingly into question. The "jōi" "expel the barbarians" portion of "sonnō jōi", changed into a reaction against the Convention of Kanagawa of 1854, which opened Japan to foreign trade. Under military threat from United States Navy Commodore Matthew C. Perry's so-called "black ships", the treaty was signed under duress and was vehemently opposed in "samurai" quarters. The fact that the Tokugawa Shogunate was powerless against the foreigners despite the will expressed by the Imperial court was taken as evidence by Yoshida Shōin and other anti-Tokugawa leaders that the "sonnō" (revere the Emperor) portion of the philosophy was not working, and that the Shogunate must be replaced by a government more able to show its loyalty to the Emperor by enforcing the Emperor’s will.