[2] The operation started on 7 June 1866 with the bombardment of Suō-Ōshima in Yamaguchi Prefecture by the Navy of the Bakufu.

The expedition ended in military disaster for the shogunate troops, as Chōshū forces were modernized and organised effectively.

By contrast, the shogunate army was composed of antiquated feudal forces from the Bakufu and numerous neighboring domains, with only small elements of modernised units.

[3] Many domains put up only half-hearted efforts, and several outright refused shogunate orders to attack, notably Satsuma who had by this point entered into an alliance with Chōshū.

[3] Tokugawa military prowess was revealed to be a paper tiger, and it became apparent that the shogunate could no longer impose its will upon the domains.