The fall of the shogunate and the Boshin War

The shogunate faced a crisis of legitimacy after signing treaties without broad consensus, an act widely viewed as a betrayal of national sovereignty. The sonno joi movement united low-ranking samurai, especially from Choshu and Satsuma, against the bakufu, while the Satcho Alliance between these two former rival domains, forged in 1866 through the mediation of Sakamoto Ryoma, brought them together against the shogunate. The bakufu's punitive expedition against Choshu that same year ended in military failure, exposing the regime's weakness, and Emperor Komei's death in January 1867, followed by the succession of the young Emperor Meiji (Mutsuhito), shifted the political balance further.