Ōtenmon Incident

Early Heian Court Politics and the Tomo and Minamoto Clans

During the Jōgan era (859-877), the Heian capital was moving toward a regime in which Grand Minister Fujiwara no Yoshifusa, maternal grandfather of the boy emperor Seiwa, effectively led the court as the supreme power. The emperor had acceded at the age of nine in 858. Yoshifusa inherited the standing of the Fujiwara Northern House, which dated back to Emperor Saga, and had succeeded in placing his daughter Akirakeiko as consort of Emperor Montoku, so that her son became Emperor Seiwa. Even as the Northern House's power grew, important ministers from other non-Fujiwara families still held key posts at court. These included Minister of the Left Minamoto no Makoto, a son of Emperor Saga of imperial origin who had been granted subject status (shinseki kōka), and Major Counselor Tomo no Yoshio, a descendant of the ancient noble Ōtomo clan and the representative of the Tomo clan.

Yoshio stood out at court as a capable administrator of considerable learning. He is said to have hoped for promotion to Minister of the Right, but that post was held by Fujiwara no Yoshimi, and the post of Minister of the Left by Minamoto no Makoto. He was also in competition with Fujiwara men who were rising as sangi. Within this balance of power at court, a major incident occurred in 866 (Jōgan 8) that shook the political history of Heian-kyō.

The Burning of the Ōten Gate and Suspicion Falls on Minamoto no Makoto

On the night of the 10th day of the intercalary 3rd month of Jōgan 8 (April 28, 866), the Ōten Gate, the main gate of the Greater Imperial Palace (Ōdairi) of the Heian Palace, was set on fire by an unknown arsonist and burned down. The Ōten Gate was a symbolic structure within the Ōdairi, used for major ceremonies such as New Year court receptions and enthronements, so its destruction was a grave matter for the court. After the fire, Major Counselor Tomo no Yoshio denounced Minister of the Left Minamoto no Makoto to Minister of the Right Fujiwara no Yoshimi as the arsonist.

Following this denunciation, Yoshimi moved to have Makoto seized by force. However, Grand Minister Fujiwara no Yoshifusa intervened, argued for Makoto's innocence, and sought to calm the situation. Through Yoshifusa's defense, Makoto escaped punishment. However, the affair greatly damaged his political credibility, and from then on he withdrew from the public stage. At this point, the true arsonist remained unidentified.

Ōyake no Takatori's Denunciation and the Fall of Tomo no Yoshio and His Son

The situation moved on the 3rd day of the 8th month of that year. A minor official of Bitchū Province named Ōyake no Takatori denounced Tomo no Yoshio and his son Tomo no Nakatsune to the court as the true arsonists of the Ōten Gate. This denunciation is also said to have stemmed from a personal feud between Takatori and one of Yoshio's retainers. Nevertheless, the court took it as an occasion to begin questioning Yoshio and his son.

During the questioning, Yoshio's retainers, after harsh interrogation, also confessed to the arson, and suspicion against Yoshio and Nakatsune deepened. It is recorded that Yoshio himself continued to deny the charge, though it is also said that he resigned himself after being told falsehoods. On the 22nd day of the 9th month of Jōgan 8, the court formally pronounced guilt on Tomo no Yoshio and Tomo no Nakatsune. Yoshio was sentenced to exile in Izu Province, and Nakatsune to exile in Oki Province. Eight members of the Tomo clan were also exiled in connection with the affair. Through this affair, the Tomo clan (formerly the Ōtomo, renamed to avoid the personal name of Emperor Junna), an ancient and renowned lineage, completely lost its political standing at court and thereafter disappeared from the forefront of history.

Fujiwara no Yoshifusa's Appointment as Regent and the Fujiwara Triumph

In handling the Ōtenmon Incident, Fujiwara no Yoshifusa played the central role and showed his political skill and influence both inside and outside the court. In the course of handling the affair, Yoshifusa, acting as guardian of Emperor Seiwa (then in his late teens), is said to have become the first subject (jinshin; a subject outside the imperial family) in Japanese history to formally hold the post of "regent" (sesshō). This was a landmark event in which the office of regent, which had been held in principle by members of the imperial family, was obtained by the Fujiwara, a single aristocratic house. It is regarded as the direct starting point of the Fujiwara regency (sekkan) politics that were established throughout the Heian period.

As a result of the Ōtenmon Incident, Minamoto no Makoto, an influential figure of imperial origin, was forced into political silence, and the Tomo clan, an ancient lineage, was completely eliminated. As a result, rival forces to the Fujiwara Northern House at court were greatly diminished, and the groundwork was laid for the line of Yoshifusa and Mototsune (Yoshifusa's adopted son, later regent and chancellor) to monopolize leadership at court. This series of events has been positioned by later historians as a representative example of the "elimination of other clans by the Fujiwara." Alongside the exile of Sugawara no Michizane (the Shōtai Incident), it has been repeatedly cited as an event symbolizing the process of Fujiwara power concentration in the Heian period.

Sources and Later Legacy

The course of the Ōtenmon Incident is recorded in official histories such as the Nihon Sandai Jitsuroku. It is also vividly depicted in pictorial form in the later picture scroll Ban Dainagon Ekotoba (a National Treasure, traditionally attributed to Tokiwa Mitsunaga), which shows the sequence of scenes from the discovery of the fire to Tomo no Yoshio's arrest. The scroll is also highly valued as an art-historical source conveying the appearance of Heian court costume, architecture, and ceremony. It shows that the Ōtenmon Incident, a political event, has gone beyond mere textual record to be passed down to later generations as an important theme in the history of Japanese art.

Significance for the History of the Japanese Sword

The Ōtenmon Incident itself was a political scandal within the court that involved no armed clash, and no record survives of swords being directly used. However, the early Heian period was an era when the technical transition from straight blades (chokutō) to curved swords (wantō), the prototype of the later Japanese sword (uchigatana and tachi), was underway. Furthermore, from this period on, as Fujiwara power concentration advanced, the court's military strength gradually shifted to a system dependent on provincial warrior classes (later the Minamoto, Taira, and others). For this reason, the Ōtenmon Incident has become an important point of reference for understanding the long-term transition in Japan from "aristocratic politics" to "the age of the warrior."