Coup of August 18

The Bunkyū Political Crisis — Chōshū's Radical Expulsion Campaign

As the Tokugawa shogunate reeled from successive political assassinations—the Sakuradamon Incident (1860) and the Sakashitamon Incident (1862)—the politics of Kyoto underwent rapid transformation. Not in Genji 1 (1864), but in the year preceding it—Bunkyū 3 (1863)—Kyoto reached the moment when Chōshū domain, at the center of the radical sonnō-jōi faction, was at the absolute height of its power.

In Bunkyū 2 (1862), Shimazu Hisamitsu, father of the Satsuma daimyo, led forces to Kyoto and pressed for shogunate reform. During this period, the Namamugi Incident occurred, raising tensions between Satsuma and the British. The shogunate implemented reforms including "relaxation of sankin-kotai" and "establishment of regent and senior councillor positions," bringing Tokugawa Yoshinobu and Matsudaira Shungaku of Echizen into shogunate governance.

In Kyoto, however, Chōshū domain began launching radical expulsion campaigns wielding the authority of Emperor Kōmei. In May of Bunkyū 3 (1863), Emperor Kōmei pressured the shogun to issue an "edict of expulsion," and the shogun set May 10 as the date of implementation. Chōshū actually fired on foreign ships passing through the Shimonoseki Straits, creating concrete proof of "expulsion in action."

At this time, Kyoto was rife with what were called "heavenly punishment" assassinations. Under the logic that "those who cooperate with the shogunate shall receive heaven's judgment," numerous individuals were killed. Officials of the Kyoto magistrate and shogunate loyalists were cut down on dark streets, their heads displayed on bridges. In the midst of this tension, Chōshū acquired such influence that it came to hold guard duties at the Imperial Palace itself.

The Night of the Coup — Sealing the Palace Gates

In the pre-dawn hours of August 18, Bunkyū 3 (September 30, 1863), Satsuma and Aizu domains acted in coordination. Having obtained Emperor Kōmei's approval through Prince Nakagawa-no-miya Asahiko, the two domains quietly secured every palace gate.

When morning came, Chōshū warriors arriving for their palace guard duty found that Satsuma and Aizu soldiers had already sealed all gates. Chōshū was barred from entering the palace and lost its voice in court affairs in a single night.

Simultaneously, the radical court nobles who had allied with Chōshū lost their freedom of action. Seven radical nobles—Sanjō Sanetomi, Sanjō Nishi Suketomo, Higashikumeno Michiyoshi, Mibu Motonobu, Shijō Takamune, Nishikoji Yorinori, and Sawa Nobuyoshi—became known as the "Seven Court Nobles." After the coup, they lost their place in Kyoto and fled to Chōshū. This "Seven Nobles Exodus" became the symbolic expression of the radical faction's political defeat.

The Architects of the Coup — Satsuma, Aizu, and Prince Nakagawa-no-miya

The coordination between Satsuma and Aizu that achieved the August 18 coup appears at first glance an unlikely partnership. How could Satsuma become Chōshū's adversary at this moment, when years later it would ally with Chōshū in the "Satsuma-Chōshū Alliance" and become the core of the anti-shogunate movement?

Satsuma pursued "public-military unity"—the path of "reforming the shogunate rather than destroying it, to create a cooperative structure with the imperial court." Believing Chōshū's radical expulsion faction unrealistic, Satsuma sought to seize control of the political situation by eliminating Chōshū's disorder. Aizu domain, holding the post of Kyoto Guardian, was responsible for maintaining security; suppressing violent chaos in Kyoto was its assigned role. Prince Nakagawa-no-miya, as the Emperor's affinal relative, provided legitimacy from within the court.

The most powerful figure orchestrating this coup was Shimazu Hisamitsu of Satsuma. Yet Hisamitsu, being not the daimyo but the daimyo's father, remained behind the scenes, issuing orders from the shadows. Matsudaira Katamori, Kyoto Guardian and daimyo of Aizu, stood publicly as the authority of the shogunate side and played the role of realizing Satsuma's intentions.

The Coup from the Perspective of Swords — The Shinsengumi and the Age of the Blade

The August 18 coup holds significant meaning in the history of Japanese sword craft. Shortly after this coup, the "Shinsengumi" began full-scale operations as an organization responsible for maintaining Kyoto's security.

The Shinsengumi was composed of a faction from the Shieikan that had come to Kyoto in February of Bunkyū 3 (1863) as the shogunate's "Rōnin Corps," and became organized as the "Mibu Rōnin Corps," then as the "Shinsengumi" in the aftermath of the coup. Commander Kondō Isami, Vice Commander Hijikata Toshizō, and First Company Commander Okita Sōji were all masters of the Tennen Rishin-ryū style of swordsmanship.

The Shinsengumi swordsmen were, in the sense of "confronting the age with the blade," the final bearers of late-Edo sword culture. Tennen Rishin-ryū was practical battlefield swordsmanship practiced by samurai of peasant origins, a style that prioritized survival in actual combat over the elegance of dojo swordplay.

The sword Kondō Isami is famous for wielding is called "Kotetsu." This blade, bearing the signature of Nagasone Koketsu, the third generation, is transmitted to later ages as the sword Kondō carried through numerous clashes, including the Ikeda-ya Incident. There are various theories about whether it was an authentic Kotetsu work, but the legend of "the greatest swordsman of the late Edo period's beloved famous blade" endures to the present day.

The Turmoil After the Coup — Toward the Kinmon Incident

Chōshū domain, expelled from Kyoto by the August 18 coup, attempted to retake the capital in July of the following year, Genji 1 (1864), launching the "Kinmon Incident" (also known as the Hamaguri Gate Incident). In this armed clash, Chōshū forces and Satsuma-Aizu troops collided, and Kyoto's streets became a scorched wasteland. Chōshū suffered great defeat and subsequently faced the First Chōshū Expedition (1864).

Yet Chōshū domain carried out military reform through the creation of Takasugi Shinsaku's "Kiheitai," and in the Second Chōshū Expedition (1866), it repelled the shogunate forces. The Satsuma-Chōshū Alliance (1866) followed, leading to the Meiji Restoration—the origin point of it all was the coup of August 18, Bunkyū 3.

Sanjō Sanetomi, who had fled to Chōshū in the "Seven Nobles Exodus," would return as one of the highest-ranking officials of the new Meiji government. History concluded the late Edo period as a drama of reversal, in which those who were driven out returned to power.