Battle of Sattatōge
Dates: The first battle occurred from the twelfth month of Eiroku 11 (1568) to the first month of Eiroku 12 (1569); the second battle occurred from 1/18 to 4/20 of Eiroku 12 (1569)
Location: Near Sattatōge (the Satta Ridge) of Suruga Province
Outcome: With the benefit of collusion from retainers of the Imagawa, the Takeda were able to breach the Imagawa defenses at Sattatōge and burn down the base of the Imagawa in Sunpu and the Imagawa residence.
The Battle of Sattatōge occurred on two occasions at Sattatōge in Suruga Province. The first battle occurred from the twelfth month of Eiroku 11 (1568) to the first month of Eiroku 12 (1569); the second battle occurred from 1/18 to 4/20 of Eiroku 12 (1569). The conflict was waged between the army of Takeda Shingen against the allied armies of Imagawa Ujizane and Hōjō Ujimasa.
The first battle occurred from 12/12 to 12/13 of 1568.
After Imagawa Yoshimoto was killed by Oda Nobunaga at the Battle of Okehazama on 5/19 of 1560, Imagawa Ujizane succeeded Yoshimoto as the head of the Imagawa, but Matsudaira Motoyasu (later known as Tokugawa Ieyasu) of Mikawa separated from the governance of the Imagawa whom the Matsudaira had served for many years. Takeda Shingen, the sengoku daimyō of Kai, altered his policy by breaking the long-standing tripartite alliance between the Takeda, the Imagawa, and the Hōjō clans and annexing the Imagawa territory of Suruga to secure access to the sea. He then entered into a secret agreement with Ieyasu and partitioned the Imagawa territory between the Takeda and Tokugawa clans at the Ōi River which defined the provincial border between Suruga and Tōtōmi Provinces.
On 12/6 of 1568, Takeda Shingen departed from his base in Kōfu and, six days later, advanced to Uchibō in the Ihara District of Suruga. Imagawa Ujizane responded by ordering Ihara Tadatane to lead an army of 15,000 soldiers to Sattatōge (the Satta Ridge) to intercept the invading forces. Ujizane himself also established a camp at the Seiken Temple. He then sent a messenger to Hōjō Ujiyasu of Sagami Province (a sengoku daimyō and father-in-law) and requested that Ujiyasu immediately deploy forces to attack the Takeda army from behind. Ujizane determined that the only means by which the Takeda army could attack the main base of the Imagawa at Sunpu was by crossing Sattatōge so by intercepting them the Takeda would be caught in-between his army and reinforcements from the Hōjō clan.
Beginning on 12/12, a battle erupted on the eastern side of the ridge, but the Imagawa forces successfully defended their location. However, the Imagawa experienced collusion among their retainers with the Takeda and Tokugawa, with twenty-one individuals (including from the Asahina and Katsurayama clans) secretly betraying the Imagawa for the Takeda. On 12/13, Ujizane felt physically endangered so he fled from the Seiken Temple to the Imagawa residence in Sunpu and then attempted to hole-up in Shizuhatayama Castle to the northwest of Sunpu. However, after those on the front lines learned of Ujizane’s withdrawal, the forces fell apart while the Takeda broke-through the ridge and pursued the retreating forces. The Takeda charged into Sunpu by the end of that same day.
Fall of Sunpu
Serving in the vanguard of the Takeda army, Baba Nobuharu quickly occupied Shizuhatayama Castle and severed the path of retreat for the Imagawa army. This destroyed the plans of Imagawa Ujizane, compelling him to flee toward Kakegawa Castle in Tōtōmi held by a senior retainer named Asahina Yasutomo. At this time, Hayakawa-dono (the daughter of Hōjō Ujiyasu and formal wife of Ujizane) could not obtain a carriage for the trip so fled on foot from Sunpu. Sunpu, the main base of the Imagawa, fell in less than a day thereafter.
Baba Nobuharu burned down the town of Sunpu and the Imagawa residence, leaving it in ruins. Takeda Shingen had ordered not to burn down the Imagawa residence because it contained multi-generational treasures, but Nobuharu purposely burned it all down including the valuables. Thereafter, when questioned about his actions, Nobuharu responded that it would be dishonorable if the Takeda were believed to have attacked Sunpu for the purpose of acquiring the valuables from the Imagawa, and Shingen is said to have understood.
Meanwhile, upon request of Imagawa Ujizane, Hōjō Ujiyasu of Sagami prepared to deploy, but, before he could complete his preparations, he learned that Sunpu fell. Ujiyasu was upset to hear that his cherished daughter, Hayakawa-dono, was forced to flee on foot from Sunpu. Later, he sent a letter to Uesugi Kenshin of Echigo stating it was difficult to bear the shame.
The second battle occurred from 1/18 to 4/20 of 1569.
Hōjō Ujiyasu ordered his eldest son, Hōjō Ujimasa, to lead an army of 45,000 soldiers from Odawara Castle, and, on 1/5 of 1569, entered Mishima in Izu Province. Ujimasa dispatched the Izu Navy to Kakegawa Castle and sent reinforcements while Ujimasa himself headed toward Sunpu by road. Having learned of these developments, the Takeda army followed in kind after the Imagawa by strengthening their position on Sattatōge with 18,000 forces so that the two armies stared down one another.
Takeda Shingen called upon Satake Yoshishige of Hitachi and Yanada Harusuke of Shimōsa to attack the territory of the Hōjō, while Imagawa Ujizane and Hōjō Ujiyasu appealed to Uesugi Kenshin of Echigo to attack the Takeda territory of Shinano. In the second month, the Takeda army launched an attack against Ōmiya Castle (aligned with the Imagawa) but retreated in the face of reinforcements from the Hōjō. In the third month, a shortage of military provisions arose. With the two sides in a relative stalemate for three months, in the fourth month, Shingen left Anayama Nobutada in Ejiri Castle and had his soldiers withdraw to Kai. Yonekura Harutsugu died in this conflict. After Hōjō Ujimasa placed numerous castles under his command, he sent forces back to Sagami and commenced negotiations with the Tokugawa.
Although the battle between the Takeda and Hōjō clans ended without a clear victor, the siege by Tokugawa Ieyasu of Kakegawa Castle held by Asahina Yasutomo (on the side of Imagawa Ujizane) was finally resolved with opening of the castle on 5/17 of 1569 through the mediation of the Hōjō clan. The Tokugawa and Hōjō then began negotiations to form an alliance. The Takeda opposed these efforts by containing the Hōjō, attacking Ōmiya Castle, and cleaned-up the Imagawa forces. The battle situation drew-in numerous daimyō from the surrounding areas, escalating to a new level.