The Otenmon Incident

A political conspiracy that occurred in 866 (Jogan 8) surrounding the burning of the Otenmon Gate, the main gate of the Daidairi Palace of the Heian Palace. Some time after the burning of the Otenmon Gate (on leap March 10), Fujiwara Yoshimi, the Minister of the Right at the time, and Tomo Yoshio, the Grand Minister of State, started the allegation that it was Minamoto Makoto, the Minister of the Left, who had set the gate on fire. The details of how this happened are not entirely clear, but one version is that they informed Fujiwara Mototsune, the Left Middle Captain of the Imperial Guard, of the incident, who then informed his foster father, Fujiwara Yoshifusa, the Grand Minister of State, and Yoshifusa defended Minamoto Makoto, or that Yoshifusa and Yoshimitsu sent troops to surround Minamoto Makoto's house, and upon learning of this, Yoshifusa investigated the truth of the incident. After this, Minamoto no Shin escaped danger thanks to Yoshifusa's efforts, but he withdrew from politics.

After this confusion, Oya Takatori, the Governor of Bitchu, claimed that the fire at Otenmon Gate was the result of a conspiracy between Tomo Yoshio and Nakatsune, father and son, and was investigated as the perpetrators of arson. Yoshio continued to deny the crime, but in the end, he was found to be the arsonist, and the father and son were exiled to Izu and Oki, and those involved were also exiled.

The truth of the incident is difficult to grasp, but judging from the political situation at the time, it appears that Fujiwara no Yoshifusa and Mototsune cleverly used the burning of the Otenmon Gate to expel Minamoto no Shin and Tomo no Yoshio from politics, first by manipulating Yoshio and others to suppress Minamoto no Shin, and later by framing Tomo no Yoshio as a criminal and driving him out of politics. Yoshifusa took this incident as a turning point to become the first commoner to become a "regent," and he devoted his efforts to the founding of the Fujiwara clan's regent system of government.

[Saeki Yuuki]

“Ban Yoshio” by Arikiyo Saeki (1970, Yoshikawa Kobunkan)”

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

866年（貞観8）平安宮大内裏(だいだいり)の正門である応天門の炎上をめぐる政治的陰謀事件。応天門の炎上（閏(うるう)3月10日）からしばらくたって、門に火をつけさせたのは左大臣の源信(まこと)であると口火を切ったのが、時の右大臣藤原良相(よしみ)と大納言(だいなごん)伴善男(とものよしお)であった。その経過は、かならずしも明確ではないが、彼らは、左近衛(さこんえ)中将参議の藤原基経(もとつね)に事の由を告げ、基経は養父の太政(だいじょう)大臣藤原良房(よしふさ)にこれを知らせ、良房が源信を擁護したとも、あるいは良相、善男が兵を発して源信の家を包囲させ、これを知った良房が事の真相を探ったとも伝えられている。こののち、良房の工作で源信は難を逃れたものの政界からは身を引いた。

　このような混乱があったのち、応天門に火をつけたのは伴善男・中庸(なかつね)父子らの共謀によるものであると、備中権史生(びっちゅうごんのししょう)大宅鷹取(おおやけのたかとり)が訴え出たため、善男父子が放火の犯人として取り調べを受けることになった。善男は、あくまでも犯行を否認し続けていたが、結局、放火犯と断定されて、父子は伊豆、隠岐(おき)に遠流となり、関係者も配流の刑に処せられた。

　事件の真相はつかみにくいが、当時の政局の動きから察すると、藤原良房・基経らが、源信や伴善男を政界から追放するために、応天門の炎上を巧みに利用して、初めは善男らを動かして源信を抑え、のちには伴善男を罪人に仕立てて政界から駆逐したとみなされる。良房は、この事件を契機に人臣初の「摂政(せっしょう)」となり、藤原氏による摂関政治の創始に力を注ぐことになった。

［佐伯有清］

『佐伯有清著『伴善男』（1970・吉川弘文館）』

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