Battle of Sakainehara
Date: 12/10 of Bunmei 10 (1478)
Location: Sakainehara in Shimōsa Province
Outcome: While details of the actual battle are scarce, Ōta Dōkan’s forces clashed with Chiba Noritane’s forces and, over the course of one day, Dōkan’s forces prevailed while Noritane fled to Usui Castle.
The Battle of Sakainehara occurred on 12/10 of Bunmei 10 (1478) at Sakainehara in Shimōsa Province. The conflict arose from an internal dispute between Ōta Dōkan (a senior retainer of Uesugi Sadamasa) and the Chiba clan, a local family of influence in Shimōsa.
In 1455, the Kyōtoku War erupted in the wake of an assassination by Ashikaga Shigeuji (the fifth Kamakura kubō) of Uesugi Noritada (the deputy shōgun of the Kantō) whereupon the Ashikaga shōgun family of the Muromachi bakufu joined with the Yamauchi-Useugi family, the Ōgigayatsu-Uesugi family, and Ashikaga Masatomo (the Horigoe kubō), in opposition to Shigeuji. Over a period of twenty-eight years, this conflict was waged across the Kantō, marking the advent of the Sengoku period in the region.
This event further triggered an internal conflict in the main branch of the Chiba clan of Shimōsa Province known as the Chiba-no-suke family. Chiba Tanenao and Chiba Tanenobu (father and son) were subject to a surprise attack at their base at Inohana Castle by members of the family, led by Makuwari Yasutane (the lord of Makuwari Castle) and a senior retainer named Hara Tanefusa (the lord of Oyumi Castle). After the fall of the castle, Tanenao and his younger brother, Chiba Tanekata, holed up in Shima Castle. Following a subsequent attack by the Makuwari and Hara forces, Tanenao fled to the Tōzen Temple whereupon he took his own life. Meanwhile, Tanenobu fled to Tako Castle. After enduring a long siege, Tanenobu finally surrendered and went to the Buddhist hall outside of the castle where he committed seppuku while reciting Buddhist incantations. This vanquished the lineage of the Chiba-no-suke family.
Meanwhile, the Hara clan (serving as the leaders among clan elders) gained more power than the head of the Chiba clan. In 1456, the Muromachi bakufu responded by ordering Ōta Dōkan (the kasai, or head of house affairs of the Ōgigayatsu-Yamauchi family) and Tō Tsuneyori (from a branch of the Chiba known as the Tō clan) to back Chiba Sanetane and Chiba Yoritane (the orphans of Chiba Tanekata) and invade Shimōsa. Sanetane and Yoritane were initially holed up in Kōnodai Castle, but, in the wake of an assault, fled to Ishihama Castle and Akatsuka Castle in Musashi Province for protection under Ōta Dōkan.
Revolt of Nagao Kageharu
Twenty years later, in the twelfth month of 1476, Nagao Kageharu raised arms from Hachigata Castle against Uesugi Akisada in regard to succession of the position of kasai, or head of house affairs, of the Yamauchi-Uesugi family. This event is known as the Revolt of Nagao Kageharu. In the first month of 1477, Kageharu stormed the main base of the Uesugi located on the plains in Ikakko in the Kodama District of Musashi and toppled Ikakko fort, causing the Uesugi to flee to Kōzuke Province. Ōta Dōkan, the head of house affairs for the Ōgigayatsu-Uesugi family, called upon Kageharu to submit to their command, but Kageharu refused. Concerned that the forces supporting Kageharu would grow stronger, Dōkan met with Akisada and Uesugi Sadamasa (the head of the Ōgigayatsu-Uesugi family) to head toward Kōzuke. On 5/13 of 1477, he brought the Yamauchi and Ōgigayatsu branches of the Uesugi together at the Ikakko fort.
Next, Dōkan adopted a plan to draw-out Kageharu. He successfully inserted soldiers in-between Kageharu’s forces, some deployed in Hanzawa and others at Kageharu’s main base of Hachigata Castle in Musashi, thereby separating the two contingents. Hurriedly seeking to return to Hachigata Castle, Kageharu’s forces clashed with Dōkan’s forces at Harigaya on the Yōdo Plain in an event known as the Battle of Yōdohara. The conflict ended in an overwhelming victory for the Uesugi forces led by Dōkan. After the defeat, Kageharu holed up in Hachigata Castle to plan for a resurgence. The Uesugi army surrounded the castle and repeatedly demanded surrender. In an effort to address his inferior position, Kageharu requested support from Ashikaga Shigeuji (the Koga kubō). In the seventh month, Shigeuji brought along dogō, or powerful clans, from across the Kantō (including members of the Yūki, the Utsunomiya, the Nasu, the Sasaki, and the Yokose clans) and marched to Taki in Kōzuke. Uesugi Akisada and Uesugi Sadamasa lifted a siege of Hachigata Castle and strengthened their defenses in Kōzuke. In the first month of 1478, a settlement was reached between the Uesugi and Ashikaga Shigeuji and, Shigeuji convinced Kageharu to return to Hachigata Castle.
Chiba Noritane, however, did not abide by the cessation of hostilities and joined with Kageharu to oppose the Uesugi clan. To subdue them, Ōta Dōkan and Chiba Yoritane arrived at Kōnodai Castle, making a clash between the two sides unavoidable, leading to the Battle of Sakainehara.
Course of events
In a lengthy letter from Ōta Dōkan addressed to Takase Minbu-Shōyū (a close associate of Uesugi Sadamasa) regarding the Battle of Sakainehara, he noted that, owing to inactivity in the Kantō, he joined forces with Yoritane to go to Shimōsa to propose to Ashikaga Shigeuji (the Koga kubō) that Chiba Noritane withdraw. With respect to the battle itself, it only notes that, on 12/10 of 1478, there was a battle at Sakainehara in Shimōsa and victory was achieved without further details.
However, according to one account, Noritane responded to Dōkan’s advance by proceeding to Sakainehara whereupon Dōkan rushed to confront him and, after a day-long battle on 12/10, Noritane was defeated and withdrew. Senior retainers of Noritane from the Kiuchi and Hara clans incurred losses in battle. According to death registers kept at the Hondo Temple, those killed in action at the Battle of Sakainehara included Sōsa Kageyu, Nojima Nyūdō, and Tsubura Sakyō-no-suke Sayuki. The Sōsa clan was a gōzoku, or wealthy family of influence, from Takada, while the Nojima clan was a gōzoku from Abiko, suggesting the large scale of the conflict.
After the defeat, Noritane sought refuge in Usui Castle. Dōkan sent his nephew, Ōta Suketada, to join Chiba Yoritane in an attack on 長躯 Usui Castle, which fell in the first month of 1479. However, a valiant counterattack by Noritane and his forces killed Suketada while Yoritane withdrew. In the confusion, Noritane also fled and the campaign ended. Thereafter, Yoritane considered another attack on Shimōsa, but many forces there supported Noritane so he declined to invade. As a result, a series of battles in Shimōsa drew to a close and the descendants of Noritane inherited the main branch of the Chiba clan.
In 1482, a settlement was reached between the Muromachi bakufu and the Koga kubō, bringing to a close the Kyōtoku War. Consequently, the conflict within the Chiba clan subsided.