Battle of Mimasetōge
Date: 10/8 of Eiroku 12 (1569)
Location: The environs of Mimasetōge in the Aikō District of Sagami Province
Synopsis: After laying siege to Hōjō Ujiyasu at Odawara Castle, the Takeda army withdrew and headed toward their home province of Kai. Hōjō Ujikuni led 20,000 forces to set-up a position at Mimasetōge on the route to Kai. In the early stages of the conflict, the Hōjō gained the upper hand, but a subsequent assault by a detached battalion led by Yamagata Masakage turned the tide in favor of the Takeda. Unable to execute a planned pincer attack with Hōjō Ujimasa, the Hōjō suffered a defeat.
The Battle of Mimasetōge occurred on 10/8 of Eiroku 12 (1569) in the environs of Mimase in the Aikō District of Sagami Province. This conflict was waged between Takeda Shingen and the Hōjō clan. This was one component of a two-front war during the Invasion of Suruga by the Takeda army.
The alliance between the Takeda of Kai and the Hōjō of Sagami and the invasion of Suruga by the Takeda
In the era of Takeda Nobutora and Hōjō Ujitsuna when the clans controlled adjacent territories, conflicts persisted in the Tsuru District of Kai. Finally, the two sides reconciled, entering into the kōsō-dōmei, or Alliance between Kai and Sagami Provinces. Later, the Imagawa clan of Suruga joined to form the Three-Party Alliance between Kai, Sagami, and Suruga Provinces. The Takeda army invaded Shinano Province and fought in northern Shinano against Nagao Kagetora (Uesugi Kenshin) of Echigo Province. The Hōjō invaded northern Kantō and also fought against the Uesugi. This spurred cooperation between the two clans to resist the Uesugi.
After the Battle of Kawanakajima, the invasion of Shinano by the Takeda clan came to an end, and the Takeda altered their strategy. In the twelfth month of 1568, the Takeda broke the alliance and launched the Invasion of Suruga against the territory of the Imagawa. This invasion precipitated the end of the alliance with the Hōjō who, in turn, entered into an alliance with the Uesugi of Echigo in opposition to the Takeda.
Encirclement of Odawara Castle
In the first month of 1569, Hōjō Ujimasa set-up a base at Sattatōge (the Satta Pass) in Suruga and confronted the Takeda forces at Okitsu. On 8/24, Shingen departed from Kōfu leading 20,000 soldiers and proceeded via Usuitōge (the Usui Pass) to Kōzuke to contain Uesugi Kenshin. Meanwhile, heading south, 1,000 troops under Oyamada Nobushige defeated a contingent of 2,000 Hōjō forces at the ancient battlefield of Todori and laid siege to the base of the Gohōjō at Takiyama Castle. After traversing the Inugoe Road, on 10/1, the forces surrounded Hōjō Ujiyasu at Odawara Castle. At this time, Odawara Castle did not yet have the well-known outer walls. Nevertheless, Uesugi Kenshin had previously been unable to topple the stronghold with over 100,000 soldiers so, instead of an assault, the besieging forces attempted to lure the defenders outside on three occasions. After the Gohōjō forces failed to come out of the castle, on 10/5, the Takeda army set fire below the castle and withdrew.
The Hōjō deployed an army for the defense of the main road to Kōshū (meaning Kai Province). Among the forces led by Hōjō Ujiteru, a contingent of 20,000 forces led by Hōjō Ujikuni in the direction of Chichibu established a position at Mimasetōge (the Mimase Pass). The Hōjō army initiated hostilities from an advantageous position against Takeda forces attempting to return to Kai Province. Moreover, Hōjō Ujimasa led over 20,000 soldiers with the aim of combining with the divisions under Ujiteru and Ujikuni to launch a pincer attack and devastate the Takeda. On 10/6, the Takeda and Hōjō armies confronted one another.
Violent clashes at Mimasetōge
Prior to the arrival of the main division led by Ujimasa, the battalions led by Ujiteru and Ujikuni took the initiative to launch an attack. Having scouted their movements in advance, Shingen divided his forces into three battalions. While contending with a frontal assault by the Hōjō army, one division held down Tsukui Castle and another division hid in the mountains to prepare for a sudden attack on the flank of the Hōjō army. On 10/8, the armies engaged in full-scale combat. At the outset of hostilities, the Hōjō had an advantage. Among the losses incurred by the Takeda, Urano Shigehide along with Asari Nobutane from the left wing were shot and killed by infantry forces commanded by Hōjō Tsunashige.
After a detached battalion led by Yamagata Masakage maneuvered to Shidatōge (the Shida Pass – approximately one kilometer to the southwest of Mimasetōge) and charged the Hōjō forces from a location of higher elevation, the situation turned at once in favor of the Takeda. Reserves for the Hōjō army such as the Naitō battalion defending Tsukui Castle in the rear were pinned down by a detached force from the Takeda led by Obata Nobusada and Katō Kagetada so were unable to come as reinforcements and incurred significant losses. After Asari Nobutane, the general for the left wing of the Takeda army, was killed in action, Sone Masatada replaced him to command the troops and succeeded in pushing back Tsunashige’s forces. Despite their disadvantageous position at the outset of the battle, in the end, the Takeda army was able to prevail.
The Takeda army headed toward a base established by the Chiba clan and yelled “The Chiba clan once fought on an equal par against the Hōjō. Aren’t you dissatisfied to be treated as their servants?” These words were said to have blunted the spirits of the Chiba.
Around the end of the battle, the main division of the Hōjō army under Ujimasa totaling 20,000 troops chasing the enemy forces from Odawara approached Ogino but after learning of their defeat at Mimasetōge, halted their advance so a pincer attack did not materialize. If Ujimasa’s forces had arrived, the Takeda army would have been subject to a pincer attack that may resulted in a major defeat for the Takeda.
Having confirmed victory, Shingen moved his army to Tanbata and held a celebratory event. Thereafter, the Takeda withdrew to Kai. In this battle, Asari Nobutane, the chamberlain of Minowa Castle in western Kōzuke was killed. In the wake of his death, Naitō Masatoyo and Naitō Masaaki (father and son) succeeded the Asari clan as the next chamberlains of Minowa Castle.
Stories concerning self-sacrifices by sword
In this battle, there are numerous stories concerning self-sacrifices by bushi in both armies.
As some of the bushi in the Takeda army withdrew to Kai, they were chased and killed by the Hōjō forces, and, in an effort to escape, went into the mountains to head toward Kai. On the route to Kai, however, they saw an ocean they did not expect to see. From the ridge, the ocean and Kai were in opposite directions. The nearest ocean was Sagami Bay. This was their mistake. The white flowers from the buckwheat fields surrounding the village appeared like the ocean. Believing that they had taken the wrong road and ventured deeply into enemy territory, the soldiers to their own lives by sword. Thereafter, out of regret for the deaths, the village residents were said to have stopped cultivating buckwheat.
In the same legend, this also occurred in the Hōjō army. While members of the defeated Hōjō fled into the mountains, they mistook the sounds caused by corn stalks after the harvest as a commotion caused by the spears of the Takeda army, and, lacking a means to escape, took their own lives. To worship the fallen soldiers, corn is not grown in this area.
Legends of the revengeful spirits of the war dead from the battle were widely transmitted in this area. There is also a legend of demons remaining from an ancillary battle at the Yabitsutōge (the Yabitsu Pass) near Mimasetōge.
Assessment of the battle
This event is known as the largest–scale mountaintop battle in the Sengoku period with differences in the elevation of respective positions a factor in the outcome.
Assessments of the battle have historically been based on the Kōyō Gunkan, a record of the military exploits of the Takeda family, compiled by a retainer of the Takeda named Kōsaka Danjō Masanobu and completed in the early Edo period. In a chronicle of the Hōjō family, the defeat of the Hōjō army is acknowledged but the losses are characterized as light (around 20 to 30 troops). After the battle, Hōjō Ujiteru sent a letter to the Uesugi family stating that he had won the battle. There is also a letter from Hōjō Ujiyasu to the widow of Buzen Yamashiro-no-kami, a senior retainer of the Koga kubō who was killed in action in this battle.
When considering only the battle itself, it appears to have been limited in scope, occurring spontaneously in the course of the withdrawal by Takeda forces. During the ensuing pursuit by the Hōjō army, Asari Nobutane, a significant retainer of the Takeda was killed while attempting to repel the Hōjō forces. In the end, although the Takeda prevailed, their army suffered significant losses as well. In the Kōyō Gunkan, the authored acknowledges that the battle was “a major victory with major losses,” posing the question as to whether the expedition requiring the army to depart from their home province in Kai was necessary.
Viewed strategically, toward the end of 1569, the Takeda toppled Kanbara Castle that had been held by the Imagawa and supported by the Hōjō and made major strides in the Invasion of Suruga. Moreover, they halted the capture by Uesugi Kenshin of Matsukura Castle in Etchū Province held by Shiina Yasutane.
Nevertheless, the real aim of Shingen with respect to the invasion of the Hōjō territory was to gain an advantage for the Invasion of Suruga. The attack by Shingen on Odawara shook the alliance between the Uesugi of Echigo and the Hōjō of Sagami and may have been a show of strength to those forces in the Kantō opposed to the Hōjō. In fact, as a condition of entering into an alliance with the Hōjō, Uesugi Kenshin was obliged to deploy forces to Shinano before 8/15 to contain the Takeda army. Even though Kenshin had vowed with a seal of blood to observe the condition, Uesugi forces were not deployed to Shinano.
In addition to contending with the war situation in Etchū Province, Kenshin complied with orders from Ashikaga Yoshiaki, the fifteenth shōgun, to enter into an alliance with the Takeda at the end of the seventh month. As a result, Kenshin intended to deploy to Shinano but sent a retainer named Ayukawa Morinaga to communicate his intention to delay the deployment. Based on this alliance, Shingen launched an invasion having taken into account that Kenshin would not deploy forces to assist the Hōjō clan. The Hōjō then sent letters to the Uesugi expressing their dissatisfaction and demanding covenants and an explanation for the failure to deploy forces. After the subsequent assault by the Takeda army on Odawara Castle and conflict continuing until this Battle of Mimasetōge, two years later, the Hōjō cut ties with the Uesugi, indirectly leading to a revival of their alliance with the Takeda clan.