Satcho Alliance

The Satsuma-Chōshū Alliance (薩摩長州同盟, Satsuma-Chōshū dōmei^?), or Satchō Alliance was a military alliance between the feudal domains of Satsuma and Chōshū formed in 1866 to combine their efforts to restore Imperial rule and overthrow the Tokugawa shogunate of Japan.

The name Satchō (薩長) is an abbreviation combining the names of the provinces Satsuma (present day Kagoshima Prefecture) and Chōshū (present-day Yamaguchi Prefecture), two of the strongest Imperialist tozama domains in Edo-period Japan.

In the 1860s, Satsuma tended to take a moderate position towards maintenance of the status quo, whereas Chōshū had become the center of an uprising aimed at overthrowing the government. Through the mediation of Sakamoto Ryōma of Tosa Domain (present day Kōchi Prefecture), Satsuma military leaders Saigō Takamori and Ōkubo Toshimichi were brought together with Katsura Kogorō (Kido Takayoshi) of Chōshū. Although the two domains were traditionally fierce enemies, their leaders agreed that the time was right for a change, and agreed in principle to assist one another in the event that either would be attacked by a third party. Also, Chōshū desperately needed modern weapons, but had very limited contacts with the western powers. Satsuma, on the other hand, had developed a substantial arms trade with Great Britain via Thomas Glover, a Scottish merchant affiliated with Jardine Matheson. At the suggestion of Sakamoto, Saigo helped broker an agreement to supply Chōshū with the weapons it needed to fight the Tokugawa shogunate.

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