Battle of Egotahara-Numabukuro
Date: 4/13 of Bunmei 9 (1477)
Location: On a plain known as Egotahara-Numabukuro in the Tama District of Musashi Province
Outcome: Toshima Yasutsune and his younger brother, Toshima Yasuaki, raised arms in support of a rebellion by Nagao Kageharu against the Yamauchi-Uesugi and Ōgigayatsu-Uesugi, but were roundly defeated by Ōta Dōkan from the Ōgigayatsu-Uesugi branch of the clan.
The Battle of Egotahara-Numabukuro occurred on 4/13 of Bunmei 9 (1477) during the early Sengoku period. The conflict was waged between Ōta Dōkan and Toshima Yasutsune in Egotahara and Numabukuro in the Tama District of Musashi Province. This was one of the limited-scale battles during an event known as the Revolt of Nagao Kageharu.
In 1476, Nagao Kageharu, a powerful retainer of Yamauchi-Uesugi Akisada, the deputy shōgun of the Kantō, joined with Ashikaga Shigeuji (the Koga kubō) in a rebellion. Early in 1477, they launched a sudden attack against Akisada and Ōgigayatsu-Uesugi Sadamasa at their base in Ikakko, causing Akisada and Sadamasa to flee after a bitter loss.
The Shiroi-Nagao family of Kageharu served as the kasai, or head of family affairs, for the family of the deputy shōgun of the Kantō. This position was held by the most senior retainer in the family over a period of two generations, including by Nagao Kagenaka and Nagao Kagenobu. The Shiroi-Nagao family wielded significant influence in Kantō, so when Kageharu raised arms, he was joined by many kokujin and jizamurai, or local lords and warriors, such as Echigo Goroshirō of Koiso Castle, Kaneko Kamon-no-suke of Ozawa Castle, Mizorogi Masashige of Mizorogi Castle, and Yano Hyōgo-no-suke of Kozukue Castle. A well-known clan from southern Musashi, the Toshima, also acted in concert with Kageharu by rebelling against the Uesugi clan.
The Toshima were members of the Chichibu family affiliated with the Bandō-Hachihei clan. In the Heian period, the Toshima were members of the Minamoto clan, participating in the Zenkunen Expedition and the Hōgen Conflict in the eleventh and twelfth centuries. The Toshima supported Minamoto no Yoritomo in a rebellion, becoming an influential family within the Kamakura bakufu. The Toshima gave rise to numerous illegitimate family lineages in Musashi Province, including the Nerima, the Itabashi, the Hiratsuka, and the Ogu clan and continued to wield considerable power in the Muromachi period. Their landholdings included the Toshima, Adachi, Niikura, and Tama districts comprising over 2,3000 hectares and 57,500 koku. In this era, the Toshima clan was headed by Toshima Kageyu-saemon-no-jō Yasutsune and resided at Shakujii Castle.
In the Kyōtoku Conflict, a war between Ashikaga Shigeuji (the Koga kubō) and the Uesugi clan (the deputy shōgun of Kantō) that ran from 1454 to 1483, the Toshima allied with the Uesugi. During this conflict, however, Ōta Dōkan, the kasai, or head of family affairs for the Ōgigayatsu-Uesugi clan, built Iwatsuki, Kawagoe, and Edo castles and significantly expanded his influence in Musashi Province. A confrontation between Dōkan and his son was the reason for the Toshima clan to act in concert with Kageharu. In particular, the construction of Edo Castle near the Toshima domain may have posed a threat to the interests of the Toshima clan. There is another theory that this was the reason that the political relationship with the Shiroi-Nagao family (who served as the head of family affairs for the Yamauchi in support of the deputy shōgun) evolved into a revolt.
Course of the battle
Toshima Yasutsune from Shakujii Castle and his younger brother, Toshima Yasuaki from Nerima Castle, raised arms, and severed the road connecting the base of Ōta Dōkan at Edo Castle from Kawagoe Castle. On 3/14 of 1477, Dōkan made plans to attack Shakujii, but these were abandoned after reinforcements from Sagami Province were unable to cross the swelling Tama River. Dōkan then promptly turned his attention toward eliminating supporters of Kageharu in Sagami. Converging with forces from Sagami, on 3/18, Dōkan attacked Mizorogi Castle, whereupon Mizorogi Masashige set fire to the castle and fled. Echigo Goroshirō of Koiso Castle surrendered.
Next, Dōkan attacked Osawa Castle, but encountered stiff resistance from the defenders. To strengthen the defenses in Musashi Province, Dōkan assigned his nephew, Ōta Suketada and Ueda Kōzuke-no-suke to Kawagoe Castle, and Uesugi Tomomasa (the younger brother of Dōkan’s lord, Uesugi Sadamasa), Miura Takahira (the older brother of Sadamasa), Kira Naritaka, Ōmori Saneyori, and Chiba Yoritane to Edo Castle. With supporters of Kageharu serving in the rear guard, Kiri Kunai、Jissōji and others toppled the stronghold of Oyamada to keep the enemy in check. In the fourth month of 1477, Yano Hyōgo-no-suke of Kozuke Castle launched attacks against Kawagoe Castle, and then, on 4/10, battled against Ōta Suketada and Ueda Kōzuke-no-suke on the Suguro Plain, where Hyōgo-no-suke incurred serious injuries and retreated.
On 4/13, Ōta Dōkan, the kasai, or head of family affairs, for the Ōgigayatsu-Uesugi clan departed from Edo Castle to shoot arrows into Nerima Castle while setting fire to the surrounding area. In response, Toshima Yasuaki, the lord of Nerima Castle, coordinated with his older brother, Toshima Yasutsune at Shakujii Castle, to launch attacks, whereupon Dōkan returned to launch counterattacks, with the enemies clashing at Egotahara-Numabukuro. At this time, Dōkan had established his main position at the Hikawa Shrine. In the end, Yasuaki along with several tens of soldiers fighting for the Toshima died in battle (or, according to one source, as many as 150 men from the Itabashi and Akatsuka clans), while Yasutsune and the other soldiers fled in defeat to Shakujii Castle. In this battle, Dōkan had set ambushes near Egotahara in advance, and with a limited number of men, antagonized the opposing force while luring them out into the open fields. Dōkan may also have deployed lightly armed foot soldiers en masse against mounted soldiers, but this is not certain.
After Yasutsune hunkered down in Shakujii Castle, on 4/14, Dōkan set-up a position on Mount Atago to confront Yasutsune. On 4/18, Yasutsune departed the castle to meet with Dōkan and propose surrender. In this period, the destruction of castles was a form of surrender, but Yasutsune did not destroy Shakujii so Dōkan considered his offer to be insincere, whereupon, on 4/21, he recommenced the attacks and captured the outer citadels of Shakujii. Yasutsune then gave up the resistance and, under cover of the dark of night, slipped away. Dōkan’s forces toppled Shakujii and restored the lines of communication with Kawagoe Castle, enabling freedom of movement. Dōkan then converged with his lord, Yamauchi-Uesugi Akisada and Ōgigayatsu-Uesugi Sadamasa in northern Musashi and turned to battle in Kōzuke, where they succeeded in containing Kageharu. In the first month of 1478, Ashikaga Shigeuji (the Koga kubō) inquired in regard to a peace settlement.
In an effort to block the settlement, Yasutsune raised arms again from Hiratsuka Castle. Dōkan, however, headed there again on 1/25 of 1478 to launch attacks, causing Yasutsune to flee toward Adachi without fighting. Thereafter, Yasutsune’s whereabouts became unknown an the main branch of the well-known Toshima family was extinguished.
Aftermath of the battle
Dōkan continued fighting in various locations to eliminate supporters of Kageharu. In the sixth month of 1480, Dōkan captured the last base of Kageharu at Kumakura Castle in the Chichibu District of Musashi, bringing to an end the conflict. In 1482, a settlement was reached with the Koga kubō, marking the conclusion of almost thirty years of conflict in the Kantō.
The former territory of the Toshima clan reverted to Dōkan who achieved significant notoriety for resolving the conflict almost entirely on own accord. However, this gave rise to jealousy from his lord, Akisada and Sadamasa. In the early autumn of 1486, Ōgigayatsu-Uesugi Sadamasa invited Dōkan to his manor in Kasuya. After taking a bath, Dōkan was cut-down and killed by Soga Hyōgo in an assassination. This event caused many of the kokujin and jizamurai formerly affiliated with the Ōgigayatsu-Uesgui branch to switch sides to the Yamauchi-Uesugi branch of the clan, triggering a break in relations between Akisada and Sadamasa that escalated into the Chōkyō Conflict enveloping the Uesugi clan for many years thereafter.