Stories of the Japanese 01618 [Muromachi/Togoku/Nagao Kageharu's Rebellion] The Battle of Sakainehara

Having obtained a promise from Shigeuji that he would not be hostile, Dōkan decided, "Then I shall strike only Kageharu," and on July 18, 1478 (Bunmei 10), he attacked the Narita camp. Kageharu was defeated with no way to counter and fled to Hachigata Castle (Yorii Town, Saitama Prefecture), but that too fell, and he retreated to Hino Castle (Chichibu City, Saitama Prefecture), located deep in the mountains.
Because Hachigata Castle was a formidable and famous fortress, Dōkan likely thought it would be troublesome if Kageharu used it again. Upon Dōkan's suggestion, Uesugi Akisada of Yamanouchi began to garrison Hachigata Castle in place of Shirai Castle.
Having seen Kageharu's defeat, Shigeuji returned to Koga on July 23. He likely had no interest in the tail he had cut off.
Now, the next target Dōkan set his sights on was the Chiba clan, a force opposed to the ceasefire agreement. As mentioned above, the Chiba family was divided into:
・The Shimōsa Chiba (father and son Suketane and Takatane) who sided with the Koga Kubo @ Usui Castle (Sakura City, Chiba Prefecture)
・The Musashi Chiba (brothers Sanetane and Yoritane) who sided with the Uesugi @ Ishihama Castle (Taito or Arakawa Ward, Tokyo)
The Shimōsa Chiba clan did not follow the ceasefire agreement and continued their military actions.
Dōkan requested permission from Shigeuji to subjugate the Shimōsa Chiba clan, specifically asking that it be done in the form of an order from Shigeuji. In other words, he would be subjugating Chiba Takatane, a vassal of Shigeuji, under Shigeuji's own orders. It is unclear whether Takatane continued the battle with Shigeuji's consent or acted independently without it, but if it were the former, Takatane, having been cut off like a tail, is truly pitiful.
Moreover, a letter of commendation issued by Shigeuji to his subordinate Abo Yasuyasu during the subsequent battle against the Chiba clan still exists. Surprisingly, it seems there were troops dispatched by Shigeuji within Dōkan's army. In other words, Chiba Takatane was attacked by soldiers sent by his own lord, Shigeuji.
Let us look at the details of the Chiba subjugation by Dōkan from here.
In November, Dōkan captured the Chiba-side Maegasaki Castle (Nagareyama City, Chiba Prefecture), and in December, he deployed his forces at Konodai (Ichikawa City, Chiba Prefecture).
Then, on December 10, a great battle took place at Sakainehara (Kashiwa City, Chiba Prefecture). Here too, Dōkan, having Chiba Yoritane on his side, defeated Takatane and forced him to retreat to Usui Castle.
At the start of the new year, on January 18, 1479 (Bunmei 11), Dōkan attacked Usui Castle but could not easily take it. Dōkan divided his forces, leaving his younger brother Suketada and Chiba Yoritane to attack Usui Castle, while he himself headed south down the Bōsō Peninsula to attack:
・Mariyatsu Takeda Nobukatsu (?-1523) of Chōnan Castle (Chōnan Town, Chiba Prefecture)
・Mariyatsu Takeda Nobuoki (1433-1511) of Mariyatsu Castle (Kisarazu City, Chiba Prefecture)
・Unakami Morotane of Iinuma Castle (Chōshi City, Chiba Prefecture)
This took half a year, and he was finally able to force their surrender on July 5.