When commodore matthew perry and the american black ships showed up in edo harbor, their appearance and subsequent "opening" of japan set off an unpredictable chain of events in tokugawa japan, chief among them a civil war that broke out fifteen years later:
the boshin war.
a) the boshin war lasted only two years, between 1868 and 1869, and pitted japanese samurai and nobles against the reigning tokugawa regime, wherein the samurai wanted to overthrow the shogun and return political power to the emperor.
b) ultimately, the militant pro-emperor samurai of satsuma and choshu convinced the emperor to issue a decree dissolving the house of tokugawa, a potentially fatal blow to the former shoguns' family.