Satsuma-Chōshū Alliance

On the 21st day of the 1st month of Keiō 2 (March 7, 1866), at the Ohanabatake residence, the Kyoto villa of the Konoe family (the lodgings of Komatsu Tatewaki), representatives of the Satsuma and Chōshū domains concluded a secret military agreement. This Satsuma-Chōshū Alliance (also called the Satsuma-Chōshū Covenant or the Satsuma-Chōshū Union) was made possible through the persistent mediation of Sakamoto Ryōma and Nakaoka Shintarō, and it laid the foundation for the overthrow of the Edo shogunate and the Meiji Restoration. It is still remembered today as one of the most dramatic and influential political alliances in Japanese history.

From Confrontation to Cooperation: The Long Rivalry Between Satsuma and Chōshū

In the early years of the bakumatsu period, the Satsuma and Chōshū domains were in fierce conflict. In the 8th month of Bunkyū 3 (1863), in the Coup of the 18th Day of the 8th Month, the Satsuma and Aizu domains cooperated to drive Chōshū's forces out of Kyoto. In the 7th month of Genji 1 (1864), in the Kinmon Incident, a combined force from Satsuma, Aizu and Kuwana repelled Chōshū's attack on the Imperial Palace. The fact that Chōshū was branded an “enemy of the court” and forced into submission by the First Chōshū Expedition was also greatly influenced by Satsuma's participation in the punitive campaign.

Meanwhile, the Satsuma and Chōshū domains had each experienced a war with a Western power, the Anglo-Satsuma War (Bunkyū 3, 1863) and the Shimonoseki campaign (Genji 1, 1864), respectively. This deepened their understanding of the military power of the Western powers, and they keenly felt the importance of Western-style weapons and training. Dissatisfaction with the politics led by the shogunate was taking shape as a foundation that aligned the two domains' underlying interests.

The Mediation of Sakamoto Ryōma and Nakaoka Shintarō

The ones who served as go-betweens for Satsuma and Chōshū were Sakamoto Ryōma and Nakaoka Shintarō, both rōnin who had defected from the Tosa domain. Ryōma studied Western-style naval affairs under the shogunate retainer Katsu Kaishū. He then established the Kameyama Shachū (later the Kaientai) in Nagasaki, engaging in shipping and arms trade. He had wide-ranging connections with patriots from Satsuma, Chōshū, Tosa and elsewhere, and he pursued his mediation from a distinctive position not bound to any particular domain or ideology.

Nakaoka Shintarō was a patriot who had also defected from the Tosa domain. He organized the Rikuentai and threw himself into the movement to overthrow the shogunate, and he had especially close ties with Katsura Kogorō (Kido Takayoshi) of Chōshū. Ryōma and Nakaoka went back and forth between the leading figures of both Satsuma and Chōshū to advance the mediation. However, a meeting planned for the intercalary 5th month of Keiō 1 (1865) at Shimonoseki was not realized, because Saigō refused just before it was to take place.

From autumn through winter of Keiō 1 (1865), Ryōma worked tirelessly to link Chōshū's problems with weapons and provisions to Satsuma's political calculations. After the First Expedition, Chōshū needed Western-style weapons (Minié rifles) for rearmament, and Satsuma was able to obtain arms through the British merchant Thomas Glover. Ryōma mediated a deal in which Chōshū would purchase weapons under the name of Satsuma, practically linking the interests of the two domains.

Conclusion of the Alliance: The Secret Agreement at Komatsu Tatewaki's Residence

From the 8th day of the 1st month of Keiō 2 (1866), talks were held at Komatsu Tatewaki's residence in Kyoto between Katsura Kogorō, representing Chōshū, and Saigō Takamori and Komatsu Tatewaki, representing Satsuma. Owing to years of conflict and mutual distrust, the negotiations were difficult and did not easily reach a settlement. Ryōma arrived in Kyoto from Shimonoseki on the 20th day of the 1st month. He was surprised that the covenant had not yet been concluded, and he brokered between the two sides.

On the 21st day of the 1st month of Keiō 2 (March 7, 1866), Satsuma and Chōshū finally reached agreement at Komatsu Tatewaki's residence. The terms of the covenant were not recorded at the time. They are known from a letter (dated the 23rd day of the 1st month of Keiō 2) that Katsura Kogorō later sent to Ryōma, summarizing the terms from memory in six articles. The main content is as follows.

1. In the event of war between the shogunate and Chōshū, Satsuma will immediately send troops to Kyoto and Osaka to put pressure on the shogunate. 2. Regardless of the outcome of the war, Satsuma will work with the imperial court to restore Chōshū's political standing. 3. Once Chōshū has cleared the stigma of being an “enemy of the court” and has been formally pardoned by the court, Satsuma and Chōshū will cooperate and work for the nation.

Ryōma witnessed this covenant. At Katsura's request, he wrote in red ink on the reverse of the letter that the contents of the six articles were accurate (dated the 5th day of the 2nd month), thereby serving as the guarantor of the covenant.

The Second Chōshū Expedition and the Proof of the Alliance

Only a few months after the conclusion of the Satsuma-Chōshū Alliance, the shogunate launched the Second Chōshū Expedition, beginning in the 6th month of Keiō 2 (1866). This time Chōshū offered direct military resistance, while Satsuma maintained neutrality and refused to join the shogunate's forces. As a result, the Second Expedition was fought on the Sekishū, Ōshima, Kokura and Geishū fronts. The Chōshū army, centered on the Kiheitai, repelled and overwhelmed the shogunate's forces, and the expedition ended in defeat for the shogunate. Coinciding with the death of Shogun Tokugawa Iemochi from illness at Osaka Castle on the 20th day of the 7th month of Keiō 2 (August 29, 1866), the shogunate was compelled to halt the campaign.

This defeat decisively undermined the shogunate's military authority, and the movement to overthrow the shogunate rapidly emerged as a realistic option. In the following year, Keiō 3 (1867), the Satsuma-Chōshū Alliance functioned as the core of the anti-shogunate forces in the return of political power to the emperor (Taisei Hōkan) and the Proclamation of the Restoration of Imperial Rule. In the year after that, Keiō 4 (1868), it played the same role in the Boshin War (Battle of Toba-Fushimi).

Swords and the Transformation of the Bakumatsu Period: What the Satsuma-Chōshū Alliance Symbolizes

The Satsuma-Chōshū Alliance also holds significant meaning from the perspective of sword culture in the bakumatsu period. The Japanese sword, regarded throughout the Edo period as the “soul of the samurai,” continued to symbolize samurai identity even in the bakumatsu period. Katsura Kogorō, Saigō Takamori, Sakamoto Ryōma and the other principal figures of the covenant were all samurai who wore the daishō. The Satsuma-Chōshū Alliance was, quite literally, a political covenant agreed upon by “samurai who wore swords.”

However, the core of the covenant lay in the military transformation toward Western-style firearm units and the Kiheitai. The weapons support that Satsuma provided to Chōshū (Western-style firearms such as Minié rifles) and the new military system that Chōshū established under Takasugi Shinsaku and the Kiheitai signified a shift toward a military system centered on modern weapons, which displaced the Japanese sword from its place as the main force on the battlefield. The Satsuma-Chōshū Alliance was also an event that institutionally and militarily prepared “the beginning of the end of the age of the samurai.”

Sakamoto Ryōma was assassinated at Ōmiya in Kyoto on the 15th day of the 11th month of Keiō 3 (1867), the year after the conclusion of the Satsuma-Chōshū Alliance. The Satsuma-Chōshū Alliance, which he had realized at the risk of his life, formed the foundation of the Meiji government after the Restoration and determined the course of Japan's modernization. In that sense, the Satsuma-Chōshū Alliance will forever be recorded in Japanese history as a turning point at which samurai who wore swords opened up a new era.