Battle of Otaihara
Date: Seventh and eighth months of Tenbun 16 (1547)
Location: Otaihara in the northern Saku District of Shinano Province
Outcome: Uesugi Norimasa dispatched forces from western Kōzuke in an effort to prevent a siege by the Takeda of Shiga Castle in Shinano. The Takeda sent forces to intercept them and achieved an overwhelming victory.
The Battle of Otaihara occurred during the seventh and eighth months of Tenbun 16 (1547) and was waged between Takeda Harunobu (the military governor of Kai Province, commonly known as Takeda Shingen) on one side and Uesugi Norimasa (the deputy shōgun of the Kantō) and Kasahara Kiyoshige (the lord of Shiga Castle in Shinano Province) on the other side.
Harunobu invaded the Saku District in Shinano and surrounded Shiga Castle. Uesugi Norimasa dispatched reinforcements to the castle but was intercepted by the Takeda army at Otaihara and crushed. Having lost hope for reinforcements, the castle fell and the Takeda garnered control of the Saku District.
In the Sengoku period, the Saku and Chiisagata districts in Shinano were contested by small and medium-sized kokujin, or provincial landowners, including the Ōi clan, the Tomono clan, the Shigeno family (such as the Unno, the Mochizuki, and the Sanada), and the Yoda clan (such as the Aiki, the Ashida, and the Kasahara).
Takeda Nobutora (the military governor of Kai Province) entered into a settlement with the Imagawa clan of Suruga and the Suwa clan of the Suwa District of Shinano. Around 1540, the Takeda commenced invasions into the Saku and Chiisagata districts. The Takeda army toppled numerous castles in the Saku District and established a forward-operating base at Maeyama Castle. In the spring of 1541, the Takeda joined Suwa Yorishige to advance forces into the Chiisagata District, capturing the main base of Ōi Sadataka at Nagakubo Castle and converted it to Suwa territory. The allied forces of the Takeda and the Suwa advanced further, and, at the Battle of Unnotaira, expelled the Unno and Sanada clans.
However, in the sixth month of 1541, Nobutora’s eldest son, Harunobu, launched a coup d’état and ousted Nobutora to Suruga Province. This event caused the subservient kokujin located in the Saku and Chiisagata districts to start leaving the Takeda. In 1542, Harunobu suddenly invaded the Suwa District and eliminated Suwa Yorishige. Ōi Sadataka used this as an opportunity to recapture Nagakubo Castle while the influence of the Takeda in the Saku and Chiisagata districts declined precipitously.
In the ninth month of 1543, after pacifying most of the Suwa District, Harunobu deployed forces to the Chiisagata District to surround Nagakubo Castle. Ōi Sadataka, along with members of the Mochizuki family, resisted from the castle, but Ashida Nobumori, Aiki Masatomo and others colluded with the Takeda and the castle fell. Sadataka was apprehended and later forced to commit seppuku.
Thereafter, Harunobu directed his forces toward the Kamiina District to fight against Takatō Yoritsugu and his allies (the Fujisawa and Ogasawara clans) who sought to gain control of the Suwa’s hereditary landholdings. During this time, Ōi Sadakiyo (Sadataka’s son) in the Saku District received support from Uesugi Norimasa (the deputy shōgun of the Kantō), summoned assorted kokujin, and revolted. On 4/17, Takatō Castle fell at the Battle of Takatō, Yoritsugu surrendered to the Takeda, and went to the main base of the Takeda in Kōfu to serve on their behalf. The Takeda then renovated Takatō Castle to use as a base for governing Shinano.
After forcing the surrender of the Fujisawa, in the fifth month of 1546, Harunobu invaded the Saku District again, surrounding Uchiyama Castle defended by Ōi Sadakiyo. After an all-out assault, the Takeda toppled the castle, and apprehended Sadakiyo.
On 2/14 of 1548, the Takeda lost to Murakami Yoshikiyo of the Chiisagata District in the Battle of Uedahara. Meanwhile, in the seventh month, the Suwa-Nishikata group launched a rebellion, shaking the Takeda’s grip on power in the district. On 4/3 of the same year, Yoritsugu returned from Kōfu to Takatō Castle. In the Kantō, Uesugi Norimasa (the deputy shōgun of the Kantō) surrounded Kawagoe Castle suffered an ignominious defeat to Hōjō Ujiyasu at the Siege of Kawagoe Castle, but the forces located primarily in Kōzuke Province remained intact.
Siege of Shiga Castle
With the annihilation of the Ōi family, the Takeda took over the majority of the Saku District, but Kasahara Kiyoshige continued to resist from Shiga Castle. Shiga was close to the border with Kōzuke, so support could be expected from the Uesugi clan (the deputy shōgun of the Kantō) via the Usui Pass. Moreover, the Kasahara had a familial relationship with the Takada clan (retainers of the Uesugi family) so the Uesugi dispatched Takada Noriyori and his son to Shiga Castle as reinforcements.
In the seventh month of 1547, Harunobu departed from Kōfu with Ōi Mikawa-no-kami in the vanguard. On 7/24, the Takeda commenced a siege of the castle and, on 7/25, the Kanehori group (a group of mining technicians utilized by the Takeda for mining as well as to construct bases and dig tunnels for attacking castles) succeeded in severing water supplies to the castle, placing the defenders in a precarious situation.
Course of the Battle at Otaihara
Uesugi Norimasa decided to dispatch military forces to serve as a rear guard for the defenders at Shiga Castle. Despite incurring a major defeat at the Siege of Kawagoe Castle in the preceding year, the Uesugi continued to maintain a powerful military force and were able to mobilize significant forces. According to a military chronicle from the Edo period, Norimasa disregarded the admonitions of Nagano Narimasa and sent a large contingent from western Kōzuke under the command of Kanai Hidekage and sixteen mounted soldiers from Kuragano Castle in the vanguard.
The forces dispatched by Norimasa traversed the Usui Pass and marched into Shinano. While in the process of laying siege to Shiga Castle, Harunobu sent Itagaki Nobukata and Amari Torayasu in a detached unit to intercept the approaching forces. On 8/6, the two armies clashed at Otaihara. The Takeda army led by Nobukata and Torayasu overwhelmingly defeated the forces sent by Norimasa, killing 14 or 15 enemy commanders and 3,000 soldiers in the battle.
Fall of the castle
As an act of intimidation, the Takeda army lined-up the heads of the 3,000 enemy soldiers killed in action to be exposed to the elements in front of Shiga Castle. Having no expectation of reinforcements, the morale among the garrison plummeted. On 8/10, the Takeda army launched an all-out assault, burning and breaching the outer and secondary enclosures. On 8/11, the Takeda attacked the main enclosure. After the killing of Kasahara Kiyoshige (the lord of the castle) and Takada Noriyori (one of the reinforcements sent by the deputy shōgun of the Kantō), the castle fell.
Harunobu imposed severe treatment of the enemy soldiers. Those taken as prisoners were made to perform slave labor while the women and children were sold-off. In battles of this era, prisoners were allocated to commanders as a form of compensation, and then sold to relatives for cash to release them from bondage. In the case of the prisoners from this battle, the price for release was very high, so most were sold-off as slaves. The wife of Kasahara Kiyoshige was given as a consort to Oyamada Nobuari (who originated from the district) for his contributions during the assault on the castle, whereupon he spirited her away to Komahashi. Her tear-filled fate is detailed in accounts compiled in the Edo-period.
After toppling Shiga Castle and taking control of the Saku District, the Takeda entered into conflict with Murakami Yoshikiyo of northern Shinano who maintained a sphere of influence in the neighboring Chiisagata District.
On 5/3 of 1547, after the Takeda commenced an invasion of the Saku District Ōi Sadakiyo attempted to resist from Uchiyama Castle, but, on 5/20, the castle fell and he surrendered. Sadakiyo temporarily served as the chamberlain of the castle, but, on 7/18, was sent to Kōfu to serve the Takeda while Uehara Iga-no-kami (Oyamada Toramitsu) replaced him as the chamberlain. Meanwhile, the surrender of Sadakiyo led to the submission by the Ichikawa clan of the Kanra District of Kōzuke Province who had been under his command, laying the groundwork for an advance by the Takeda into Kōzuke.
In the second month of 1548, Harunobu invaded the Chiisagata District and fought against Murakami Yoshikiyo at Uedahara, but he lost senior retainers including Itagaki Nobukata and Amari Torayasu, incurred a major defeat at the Battle of Uedahara.