Year: Chōroku 3 (1459) to Bunmei 9 (1477)
Location: Irako near the Tone River in Musashi Province
Outcome: Uesugi Fusaaki established a base in Irako from which to conduct a prolonged war against Ashikaga Shigeuji (the Koga kubō) which was finally settled.
The Irako War occurred from Chōroku 3 (1459) to Bunmei 9 (1477) and was waged between Ashikaga Shigeuji (the Koga kubō) and the Uesugi clan (the deputy shōgun of the Kantō) in the Irako area of Musashi Province. This was a subset of the broader conflict known as the Kyōtoku War – a conflict involving the ruling Ashikaga family, the Kamakura kubō, and several branches of the Uesugi family that spanned over twenty-eight years from 1454 to 1483. The Irako War is also used to refer to the large-scale battle that occurred in 1477 at the end of the long war.
Beginning in 1454, the Kyōtoku War showed indications of becoming an extended conflict. After having been ousted by the Uesugi, Shigeuji began counterattacks while based at his palace in Koga in Shimōsa Province. This served to divide the Kantō along the Tone River, with the east side being the faction of the Koga kubō (the Koga army) and the west side being the faction of the deputy shōgun of the Kantō (the Uesugi army). In particular, in northern Kantō, the Koga army operating from the direction of Shimotsuke Province pressured the base of the Uesugi clan in Kōzuke Province. In southern Kantō, the Uesugi army operating from the direction of Musashi Province pressured the base of the Koga kubō in Shimōsa Province. As a result, with respect to both sides of the conflict, control of the Tone River basin in the area between their camps was deemed extremely important as a means to alleviate the military pressure from the enemy on their respective camps.
On 9/17 of Kōshō 2 (1456), the Koga army and the Uesugi army clashed on the Okabe Plains of Musashi along the Tone River. Around this time, in the Tone River basin, Oshi, Fukaya, and Sekiyado castles were constructed.
Battle of Ōta-no-shō
In 1459, Uesugi Fusaaki (the deputy shōgun of the Kantō) built a fort in Irako and assembled commanders including Uesugi Mochitomo (shugo daimyō), Uesugi Fusasada (shugo daimyō), Uesugi Norifusa, and Uesugi Masafuji. Upon hearing this news, Ashikaga Shigeuji charged out to attack Irako. On 10/14, the two armies clashed at Ōta-no-shō. Fusaaki’s forces incurred losses including, among others, Uesugi Norifusa.
After learning that Iwamatsu Iezumi and Iwamatsu Mochikuni of Kōzuke had joined the Uesugi army, Fusasada and Masafuji traversed the Tone River and launched an attack at Hanetsugu-hara and Ebise-guchi against the Koga army which had set-up an encampment on the Kōzuke side of the river, but the attacking forces lost again. The Uesugi army incurred a major blow, but the Koga army also retreated so Irako was secured by the Uesugi. Thereafter, Fusaaki made a base in this location from which to prosecute a long war.
The Muromachi bakufu intended to dispatch reinforcements to Irako, but Shiba Yoshitoshi was held responsible for triggering an internal rebellion known as the Battle of Chōroku and banished so the reinforcements were not forthcoming.
Ashikaga Masatomo was the older brother of a different mother of Ashikaga Yoshimasa (the eighth shōgun of the Muromachi bakufu). Upon demand of the Uesugi clan, Masatomo intended to go to Izu Province to serve as the new Kamakura kubō. The Uesugi family, however, had not reached an internal consensus of opinions as to whether to accept Masatomo so he stayed in Horigoe in Izu and adopted the title of the Horigoe kubō. Uesugi Norimasa (the son of Uesugi Noritomo and grandson of Uesugi Ujinori) who served Masatomo believed that the expulsion of Shigeuji was the most convincing argument for Masatomo to enter Kamakura so, in 1465, deployed from Izu. He then converged with Uesugi Fusaaki (the deputy shōgun of the Kantō) and Uesugi Fusasada (the military governor of Echigo), and his son, Uesugi Akisada, and headed toward Irako.
The Muromachi bakufu ordered Imagawa Yoshitada of Suruga and Takeda Nobumasa of Kai (both military governors) to send reinforcements to Masanori, but, prior to the arrival of these forces, the Koga army seeking to crush the Uesugi army advanced against from Ōta-no-shō to Irako. However, on 2/12 of Bunshō 1 (1466), Uesugi Fusasada suddenly died in Irako and did not have a child to be his heir so Akisada was immediately adopted to succeed him as the deputy shōgun of the Kantō. This led to a temporary cessation of the fighting.
Battle of Irako
Thereafter, in the midst of standoffs and skirmishes persisted in Irako between the Koga army and the Uesugi army, back-and-forth battles between the two sides unfolded across the Kantō. In 1473, Nagao Kagenobu, the kasai, or head of house affairs of the Yamanouchi-Uesugi family (the deputy shōgun family of the Kantō) died. Then, Uesugi Masazane of the Ōgigayatsu-Uesugi family was killed in action in Irako by the Koga army. These events led to a sudden change in the situation. After failing to become the successor to the role of head of house affairs, Nagao Kageharu (Kagenobu’s son) grew resentful toward Uesugi Akisada, switched his allegiance to Ashikaga Shigeuji, and rebelled. This event is known as the Revolt of Nagao Kageharu.
In 1476, Kageharu surrounded the area of Irako where the troops of the Yamanouchi-Uesugi army were stationed. Akisada could not call upon reinforcements because Uesugi Masanori and Ōta Dōkan had led the main divisions of the Horigoe kubō army and the Ōgigayatsu-Uesugi army to Suruga Province to mediate a dispute within the Imagawa clan. On 1/18 of Bunmei 9 (1477), Irako Castle fell while Akisada narrowly escaped back to Kōzuke. This marked the end of the long period during which the Yamanouchi-Uesugi maintained a base in Irako.
Thereafter, Ōta Dōkan, the lieutenant to Uesugi Sadamasa (the head of the Ōgigayatsu-Uesugi family) took the lead in suppressing the rebellion by Kageharu. Witnessing these developments, Akisada became concerned at the rising prominence of the Ōgigayatsu-Uesugi family and sought to reconcile with Shigeuji. The war situation then gradually evolved into a competition between the Yamanouchi-Uesugi and the Ōgigayatsu-Uesugi families.