The Sakashitamon Gate Incident

The Bakumatsu's Greatest Crisis—The Collision between the Kōbu Gattai Path and the Sonnō-jōi Faction

When Ii Naosuke, who had persecuted the sonnō-jōi faction during the Ansei Purge of 1859, was assassinated in the Sakuradamon Gate Incident of March 1860 (Ansei 7), the Edo Bakufu faced a severe loss of authority. The senior councilor Andō Nobumasa of the time promoted a bold policy called 'kōbu gattai' (union of court and bakufu) to overcome this crisis.

Kōbu gattai was a policy of uniting the imperial court (kō) and the bakufu (bu) to address the sonnō-jōi problem, and as a symbolic measure, it was decided that Kazunomiya, sister of Emperor Kōmei, would be married to Shogun Tokugawa Iemochi. In October of Bunkyū 1 (1861), Kazunomiya left Kyoto and descended to Edo.

However, this marriage of Kazunomiya provoked fierce opposition from the sonnō-jōi faction. The logic that 'giving an imperial princess to a bakufu that invited foreigners into the country would be a national disgrace' led to increasing calls that the kōbu gattai policy was disrespectful to the imperial family and a treasonous act that would cost Japan its independence. The Mito domain's sonnō-jōi faction in particular opposed it strongly.

The Mito domain was an ideological flashpoint of the bakumatsu period. Mito learning, known for the compilation of the 'Great History of Japan' (Dai Nihon Shi), fostered an intense ideology that regarded the emperor as Japan's legitimate sovereign and held that foreign invasions should be repelled by the sword. The adherents of this ideology scattered throughout the country as rōnin and pursued radical measures to assassinate bakufu leaders.

January 15, Bunkyū 2—The Surprise Attack at Sakashitamon Gate

On January 15, 1862 (Bunkyū 2), along a road outside the Sakashitamon Gate of Edo Castle, where the morning cold lingered. The procession of Andō Nobumasa, a senior councilor, was heading toward Edo Castle. Andō was the daimyo of Iwaki Taira domain (present-day Iwaki City, Fukushima Prefecture) with a stipend of 50,000 koku, and as a central figure in the kōbu gattai policy, he controlled bakufu politics.

Suddenly, six men slashed into the procession. They were Mito domain retainers and rōnin who had abandoned the domain, with Kōno Kenzō reported as the ringleader. Drawing their swords and slashing at the escort warriors, they closed in on Andō Nobumasa himself.

The escort warriors desperately fought back. Before Edo Castle itself, a fierce battle unfolded in which the crimson blood of swords stained the white snow. Though Andō Nobumasa was wounded in the back (or shoulder, according to some accounts), he barely managed to escape into his palanquin and narrowly avoided death.

All six assailants were either killed on the spot or took their own lives. In this battle, the escort warriors also suffered casualties.

A Failed Assassination—Yet Why the Bakufu Was Wounded

In the Sakuradamon Gate Incident, Ii Naosuke was completely assassinated. In the Sakashitamon Gate Incident, Andō Nobumasa survived. So was the Sakashitamon Gate Incident merely a failed event?

Not at all. Andō Nobumasa certainly did not die. However, within months of the incident, he was forced to resign from his position as senior councilor. The logic that a wounded senior councilor remaining in office would undermine 'bakufu prestige' led to his position within the bakufu rapidly deteriorating.

A more fundamental issue is the political significance of the fact that 'the bakufu's central authority was attacked by the sonnō-jōi faction once again.' By the Sakashitamon Gate Incident occurring following the Sakuradamon Gate Incident, the bakufu impressed upon both domestic and foreign audiences a sense of helplessness: 'Tokugawa military power cannot suppress the sonnō-jōi faction.'

The authority of the bakufu had been protected by the sword. The reality that the swords of warriors escorting the shogun's procession and the swords of the senior councilor's guards did not function (or could not function) shook the very foundation of the Tokugawa system that had endured for over 250 years.

From the Perspective of Swords—Bakumatsu Swords and the Return to Actual Combat

The Sakashitamon Gate Incident is also an event that marks an important turning point in Japanese sword history. The Ansei and Bunkyū periods (1850s–1860s) were an era when the 'return to actual combat' of the Japanese sword was at issue.

From the mid-Edo period onward, as centuries of peace continued, the Japanese sword took on an increasingly decorative character as a 'symbol of the warrior,' and many beautiful works were created without the premise of being wielded in actual combat. However, as the turmoil of the bakumatsu period approached, demand for 'a sword that could actually cut down a person' rose rapidly.

A notable swordsmith of this era is Kiyomaro, also known as Yamaura Kiyomaro. Active during the bakumatsu turmoil, Kiyomaro revived the techniques of the ancient Soshu school and forged swords that combined practical cutting ability with aesthetic perfection. The swords of Kiyomaro, called the 'sage of swords in the bakumatsu era,' were emblematic of the 'sharp and beautiful blade' that warriors aspired to.

While specific records do not survive regarding the swords carried by the Mito rōnin who participated in the Sakashitamon Gate Incident, the sword culture of the Mito domain deserves attention. The Mito domain had a spirit where scholars and swordsmen were unified, and sword practice and the sonnō ideology were inseparably linked. The 'sword of Mito activists' was emblematic of the bakumatsu spirit that unified ideology and action.

Andō Nobumasa's Fall and the Limits of Kōbu Gattai

Immediately after the Sakashitamon Gate Incident, Andō Nobumasa's political position rapidly deteriorated. Criticism of a wounded senior councilor continuing public duties, pressure from opponents of Kazunomiya's marriage, and further intensification of the sonnō-jōi movement combined to force Andō to resign from his position as senior councilor in April of Bunkyū 2 (1862).

The kōbu gattai policy failed, and instead, the competition intensified between powerful domains such as Satsuma, Chōshū, and Tosa and the bakufu over political hegemony in Kyoto. The Sakashitamon Gate Incident was a watershed demonstrating that the bakufu could no longer control domestic political violence on its own.

Thereafter, bakumatsu politics moved away from Edo and unfolded primarily in Kyoto. The conflict between the anti-bakufu movement sheltered under imperial authority and the kōbu gattai line would eventually lead to the Boshin War, a civil conflict.

Sakuradamon and Sakashitamon—What Successive 'Sword-Driven Political Upheavals' Changed

The flow from the Sakuradamon Gate Incident (1860) to the Sakashitamon Gate Incident (1862) demonstrates the establishment of an 'assassination culture by sword' in bakumatsu politics. These two incidents symbolize a transition from a society that was ostensibly a 'peaceful era of good rule' throughout the Edo period to an age when the sword actually began to function once again as an instrument of political violence.

This era, in which the sword transformed from 'the soul of the warrior' into 'a tool of revolution,' would come to an end with the Edict on Abandoning Swords (haitorei) in 1876. The Sakashitamon Gate Incident is an important chapter in that process and a testament to living in the turbulent age when the Japanese sword last occupied the center of history.