Battle of Seki and Kajita
Oda-Kajita Allied Army
Nagai-Hida Allied Army
Date: Eighth and ninth months of Eiroku 8 (1565)
Location: The Chūnō area (central portion) of Mino Province
Synopsis: After Saitō Tatsuoki inherited the headship of the Saitō clan, Oda Nobunaga launched an invasion of the central portion of Mino in furtherance of a plan to wrest control of the province away from the Saitō. Local lords aligned with the Saitō, including Nagai Michitoshi of Seki Castle and Kishi Nobuchika of Dōhora Castle, joined in opposition to the Oda. In this event, Michitoshi led a surprise attack against the Oda army during their return to Inuyama. This plan, however, failed as Oda reinforcements led by Saitō Toshiharu (aligned with the Oda), along with betrayals on the side of the Nagai forces, led to the loss of Seki and Kajita castles to the Oda.
The Battle of Seki and Kajita occurred in the eighth and ninth months of Eiroku 8 (1565) in the central portion of Mino Province. The conflict was waged between allied forces led by Nagai Michitoshi and Hida Tadamasa (backed by reinforcements from Saitō Tatsuoki) against allied forces led by Satō Tadayoshi, Satō Tadayasu, and the Kajita group (backed by reinforcements from Saitō Toshiharu aligned with the Oda). This was one of the major events to occur during the Invasion of Chūnō by which the Oda garnered control of the central portion of Mino Province.
After the Battle of Dōhora on 8/28 of Eiroku 8 (1565), Oda Nobunaga spent one night at the residence of Satō Tadayoshi in Kajita Castle. On 8/29, below the castle, Nobunaga conducted an inspection of the heads of Kishi soldiers taken during the battle. Thereafter, while Nobunaga was en route to Inuyama on the border of Owari and Mino, Nagai Michitoshi departed from Seki Castle and converged with reinforcements led by Saitō Tatsuoki from Inokuchi forming an army of over 3,000 soldiers to launch an attack against the Oda. Nobunaga was accompanied by only 800 troops. Outnumbered, the Oda retreated to an open field to regroup, and, after feigning and attack, retreated to Unuma. Michitoshi appeared poised to attack Kajita so Nobunaga hurriedly appointed Saitō Toshiharu to serve as the commander of a battalion of 500 soldiers and dispatched them as reinforcements.
Course of events
The Kajita forces were comprised of a total of 1,000 archers and arquebusiers, split into two battalions. The Kinumaru southern entrance to Kajita Castle was secured by two generals: Saitō Toshiharu and Satō Tadayasu (the eldest son of Satō Tadayoshi) while Tadayoshi defended the rear entrance to the northeast.
The Nagai forces grouped all together and pressed toward the Kinumaru watchtower. While riding a horse on the battlefield to give orders, Satō Tadayasu was shot by an arrow and died, darkening prospects for the Kajita forces. At this time, Yuasa Sanuki from the Kajita forces stepped-up and, wielding a spear, charged the Nagai forces and gained the upper hand, forcing the Nagai forces back to the banks of the Hida shallows and enabling a victory. After the battle, Saitō Toshiharu recognized Sanuki for his valor, presenting him with a sword and granting him one of the characters from his name (Shingo), after which he adopted the name of Yuasa Shinroku.
Hida Tadamasa traversed the Sugihora Pass and pressed forward from the east, leading to a clash against Satō Tadayoshi near the Kawaura River. After the Seki army lost and pulled-back, Tadayoshi proceeded straight forward, engaging in four or five clashes and driving-back the Hida forces to the Kawaura River which served as a natural moat. He also prevailed in battle to the northeast of Kajita Castle. According to one account, Tadamasa was killed in this battle, but there is a high likelihood that was an imposter to deceive the opponents.
Saitō Toshiharu had his men and horses rest at Kajita Castle and then appealed to Nobunaga for the dispatch of reinforcements on the grounds that if he did not occupy Seki Castle at once, it would become an impediment to a later invasion of Mino. Nobunaga acknowledged his view and swiftly sent reinforcements.
During the assault on Seki Castle beginning in the ninth month, Toshiharu led Kajita forces from the east while reinforcements from Nobunaga attacked from the south and west. Nagai Michitoshi mounted a defense from fortresses built in the environs of Seki Castle as well as through deceptive tactics, but the reinforcements from Saitō Tatsuoki did not arrive in time and, before long, was compelled to abandon Seki Castle.
It is surmised that Michitoshi did not resist until the end because Seki Castle was not fortified to the extent necessary to enable the defenders to ward-off an assault in addition to the fact that some of the individuals in the castle such as Habuchi Yoshimasa colluded with Nobunaga.
Seki Castle was abandoned and placed under the command of Mori Yoshinari, the lord of Kaneyama Castle in the Kani District of Mino. Upon orders of Nobunaga, Saitō Toshiharu (Nobunaga’s younger brother-in-law and a close relative of Saitō Dōsan) was adopted by Satō Tadayoshi, an influential kokujin, or provincial landowner, in Mino. Toshiharu wed Tadayoshi’s daughter named Seishitsuin. As the heir to the Mino-Saitō family, Toshiharu inherited the role as the lord of Kajita Castle in a strategic location in Mino. Meanwhile, the band of retainers who served Satō Tadayoshi known as the Kajita group became the elite guards of Toshiharu while members of the Mino-Satō clan became the relatives and security officers of Toshiharu. After becoming the second-generation lord of Kajita Castle, Toshiharu requested his older brother, Saitō Toshitaka, protect the castle in his absence.