Edo Castle Incident
The Edo Castle Incident occurred in the late Muromachi period, in the winter of Bunmei 18 (1486) at Edo Castle in Musashi Province. In this incident, Uesugi Sadamasa of the Ōgigayatsu-Uesugi family ousted Ōta Sukeyasu, the lineal heir of Ōta Dōkan, from his base at Edo Castle following the assassination of Dōkan by retainers of Sadamasa.
Owing to a lack of authenticated accounts, the details of this incident are uncertain. The only known reference regarding this incident is in a compilation of poems created by a monk named Banri Shūku who, upon the invitation of Dōkan, resided in Edo Castle and was on friendly terms with Uesugi Sadamasa and Ōta Dōkan. In this compilation, there is a reference to a poem deemed written in the first month of Bunmei 19 “at the event hosted by Shuri-no-daibu (= Sadamasa) after the conflict in Edo Castle.” Similarly, a seven-syllable quatrain for the farewell of an individual call Kiun who decided to leave Edo after the demise of Dōkan refers to a battle in the castle before the season for the blossoming of apricots (the twelfth month in the lunisolar calendar) and a replacement of the lord of the castle.
In the eighth month of 1486, Dōkan was assassinated by Sadamasa’s retainers at the Kasuya residence in Sagami where Dōkan had served under Sadamasa. Sukeyasu subsequently returned to Edo Castle and inherited the headship of the clan. Prior to the twelfth month (in the winter), conflict erupted inside Edo Castle. As a result, Sukeyasu was banished while Sadamasa is surmised to have replaced him as the next lord of Edo Castle. After fleeing to Kai Province, Sukeyasu was assisted by members of the Yamanouchi-Uesugi family and joined their camp during the Chōkyō War. Until his return to Edo Castle around 1505, Sukeyasu spent approximately twenty years in exile.