In 1554, the greatest three powers on Japan’s Kanto plain, the Imagawa, Takeda, and Hojo, put aside their mutual hostility to focus on other matters outside the Kanto. This alliance made possible three events: First, it allowed the Imagawa to make their fateful advance on Kyoto. Second, it allowed the Takeda to focus on Shinano. Third, it allowed the Hojo room to deal with the Uesugi.
To understand this agreement, we must go back to 1536. In that year Imagawa Ujiteru, the Lord of Suruga, died suddenly and lacked any sons. His brothers, including several who were serving as priests in Buddhist temples, all fought to succeed him. The Takeda of Kai and the Hojo of Sagami both took an interest in this fight (which was called the Hanagura Incident) and backed the capable fifth brother. This man took the name Imagawa Yoshimoto on his victory in 1537. Yoshimoto then married the eldest daughter of the Takeda clan head Takeda Nobutora, turning previous diplomacy on its head.
The Imagawa and Hojo had been close allies for decades by this time, and the Hojo daimyo Hojo Ujitsuna took offense at this perceived snubbing. Yoshimoto also negotiated the marriage of Takeda Harunobu (the future Shingen) to a noblewoman of the Imperial Court (a daughter of Sanjo Kimiyori). This arrangement was a return-in-kind for the marriage of Harunobu’s sister. Thanks to Satomi aggression, the Hojo would not act on the Imagawa realignment until 1539 by seizing territory on the western bank of the Fuji River. At the same time affairs in Kai changed dramatically.
While a talented ruler, Takeda Nobutora was not popular. Now considered to have suffered from some form of mental instability, Nobutora was a harsh, intemperate man who governed according his arbitrary designs. His retainers tolerated this for as long as it benefited them and the clan. For all his faults, Nobutora had succeeded in rebuilding the fortunes of the Takeda and unified the province of Kai. However, in 1540 he pushed them over the edge by announcing the deposition of his eldest son in favor of a younger one, Nobushige.
This was unacceptable to the retainers and Nobushige alike, as the latter remained loyal to his brother. Imagawa Yoshimoto got wind of this and supported his brother-in-law, as potential instability in Kai was not in the best interest of Suruga. So Harunobu, his guardian Obu Toramasa, and other senior Takeda retainers, plotted the downfall of Nobutora. While the details of the coup are unclear by 1541 Takeda Nobutora was living in exile in Imagawa lands, at the expense of Yoshimoto and Harunobu was lord of Kai. Harunobu paid back the debt in part by supporting the Imagawa during the Kitsunebashi campaign against the Hojo in 1544. By that time, Ujitsuna had died and was succeeded by his brilliant son Ujiyasu.
Hojo Ujiyasu of Sagami. See page for author [Public domain], via Wikimedia Commons.
Under new leadership, Takeda made significant inroads into Shinano. In 1542, Harunobu defeated a major alliance of Shinano lords at the battle of Sezawa. The Suwa, Kiso, and Tozawa (in a separate campaign) clans were all absorbed. The Takato followed in 1545, and it appeared the Takeda would conquer the province shortly. The situation changed in 1548 when the Murakami dealt the conquerors a bloody nose at Uehara. When the Murakami and their allies the Ogasawara had been pushed out of Shinano in 1552, they fled to Echigo and the shelter of Nagao Kagetora (the future Kenshin).
The Imagawa had similarly become preoccupied with Mikawa and Owari. Nominally under the control of the Matsudaira clan, Mikawa had fractured after the death of Matsudaira Kiyoyasu in 1536. The Matsudaira themselves were similarly divided. The chaos opened the way for the invasions of Oda Nobuhide of Owari. Nobuhide (the father of the famous Nobunaga) was a talented and aggressive commander. His aggression would earn him the nickname “Tiger of Owari”. Nobuhide began by taking the Matsudaira stronghold of Anjo in 1540 in a lightning invasion. This sent the young lord of the Matsudaira, Hirotada, to the Imagawa for support.
Yoshimoto moved to intervene and sent an army commanded by his uncle, the monk-general Taigen Sessai into Mikawa. The resulting struggle lasted most of the decade. Eventually Taigen Sessai was able to defeat Nobuhide at 2nd Azukizaka in 1548. The following year, Hirotada died. Control passed to the Imagawa through the future Tokugawa Ieyasu, a child. Oda Nobuhide then died in 1551, causing a civil war in Owari.
Meanwhile in the east, the Hojo contended against the Uesugi and Satomi. In 1545 Hojo Ujiyasu and his brother Tsunanari won one of the finest victories of the era at Kawagoe. Defeating the combined forces of the allied Uesugi branch families (the Ogigayatsu and Yamanouchi) and the eastern Ashikaga in the process. The Hojo went on the offensive, and within a few years the Ogigayatsu Uesugi had been eliminated, the eastern Ashikaga contained and rendered toothless, and the Yamanouchi Uesugi struggling in Kozuke.
In 1551, Ujiyasu took the Uesugi fortress of Hirai and evicted them from Kozuke. Uesugi Norimasa, Lord of the Yamanouchi, fled to Echigo. Nagao Kagetora soon proved to be a problem for the Hojo, leaving them unable to secure Kozuke. To counter the Nagao, the Hojo were forced to divide Kozuke with the Takeda. To the east, the Satomi continued to pester the Hojo, and Ujiyasu was hard pressed to do anything about them.
With all three lords now confronted by situations that required their attention to be elsewhere they decided to settle the matter of their shared border by diplomatic means. Such an agreement would not have been without precedent. In 1545, the Takeda had proposed a truce that allowed the Imagawa and the Hojo the breathing room needed to deal with concerns in Mikawa and at Kawagoe.
In 1554, Yoshimoto, Ujiyasu, and Harunobu all met at Zensho Temple under the watchful eyes of Taigen Sessai. At the monk’s insistence, a network of marriages was arranged. Hojo Ujiyasu would wed his daughter to the heir of the Imagawa and his heir in turn was married to Harunobu’s daughter. In 1552 a prior arrangement had seen the heir of the Takeda wed to Yoshimoto’s daughter. Sessai further negotiated a mutual cease-fire between the factions and vows made for mutual reinforcement and support. Thus settled, the Three Provinces (named for Kai, Sagami, and Suruga) Alliance allowed each clan to focus on affairs outside the Kanto.
The Imagawa turned their eyes on Owari. Nobuhide had been succeeded by his second son, Nobunaga, who was an unlikely choice in the eyes of the neighboring lords. Nobunaga in his youth put on an elaborate act conducting himself in the most shocking manner possible to traditional mores. The charade ended in 1553 when an elder retainer had committed suicide out of shame, and Nobunaga took on a more acceptable, though still eccentric, manner. Imagawa Yoshimoto laid plans to deal with the Oda as his ambitions for Kyoto grew, which was derailed by the death of Taigen Sessai in 1557. By this time, he had come to depend on the talents of a maturing Ieyasu, now known as Matsudaira Motoyasu. The Imagawa campaign for Owari started the following year in 1558 with the fall of Terabe Castle. It ended with the ambush at Okehazama, the death of Imagawa Yoshimoto, and the catapulting of Oda Nobunaga to national prominence in 1560.
The Grave of Imagawa Yoshimoto of Suruga at Okehazama. By Lombroso (Photo taken by Lombroso) [Public domain], via Wikimedia Commons
Power then passed to Imagawa Ujizane, Yoshimoto’s heir. However, Ujizane was a weak and politically inept leader, and before long he had alienated many of his father’s retainers. Fatally, among those included was Matsudaira Motoyasu. The young lord of Mikawa broke away from Imagawa control in 1561 by tricking Ujizane into releasing the Matsudaira hostages in Suruga. With the Matsudaira gone, the Imagawa turned to the Asahina clan for support. Under their influence, Ujizane executed many of his retainers, and the Imagawa fell into decline.
The Takeda turned to greater ambitions. While his allies took care of their concerns, Harunobu could resume his march into Shinano. In 1553, the Murakami and Ogasawara returned in force with the support of Nagao Kagetora and the two forces clashed for the first time at Kawanakajima. Eventually, the two warlords would fight five times over that ground. The battle ended in a stalemate though technically the Takeda came away a little worse. In any event, Harunobu’s ambitions had been checked. Eventually, he would triumph by conquering Shinano in 1564, but it came at a price through the constant skirmishes at Kawanakajima, especially the pitched 4th battle in 1561. Shingen (he had taken that name in 1559 on entering the Buddhist priesthood) then turned to Kozuke and Hida, and military action there would occupy him for much of the decade.
Takeda Harunobu of Kai, AKA Shingen. By 日本語: 不明 English: Unknown [Public domain], via Wikimedia Commons.
Internal problems would also plague the Takeda during those years. In 1560, a plot led by Shingen’s cousin Katanuma Nobumoto was uncovered, resulting in the conspirator’s death. There was a second plot in 1565, this time led by Obu Toramasa and Shingen’s heir Yoshinobu. Toramasa was forced to commit suicide while Yoshinobu was confined to Toko Temple. Two years later he died under unclear circumstances; though it seems likely his father forced him to commit suicide. These events placed great strain on the Three Provinces Alliances, as Imagawa Ujizane did not take well to the news of his sister’s disgrace, and the Hojo supported him.
For the Hojo, the alliance proved less advantageous. Already checked in Kozuke by the Nagao and with the Satomi blocking his expansion further east, Hojo Ujiyasu was left with little option in where to expand. So he turned inward, refining and extending a line of castles and their networks of satellite castles that served to protect Odawara and the Hojo domains. In 1559-1560 events in Echigo saw the rebirth of the Uesugi when Uesugi Norimasa adopted Kagetora, who took to his new role and name (Uesugi Masatora) with vigor. He also assumed the title of Kanto Chancellor.
The Uesugi struck into Kozuke with the Satomi in 1560 and continued to push inwards through the following year. During this Ujiyasu stepped down as lord of the clan, passing the title to his son Ujimasa, but in reality the elder Hojo remained in control.
The Uesugi advance went up to the walls of Odawara itself and succeeded in burning the castle town, but they were turned back after two months by logistics problems and the Hojo defenders. However, Masatora was able to score a propaganda victory by visiting the Tsurugaoka Hachiman Shrine at Kamakura. There, he announced his assumption of the Uesugi patrimony and entered the Buddhist priesthood, taking the name Kenshin. From here on for the next eight years Hojo and Uesugi would clash across the Kanto, the conflict finally ending until 1569 when Ujiyasu arranged for his 7th son to be adopted by Kenshin. In the meantime, Ujiyasu triumphed in the 2nd Battle of Konodai in 1564 against the Satomi, and Hojo forces entered Shimosa and Kazusa. However, the Satomi were not entirely defeated, continuing the feud.
By 1568, it was clear the Three Provinces Alliance had collapsed. However, Shingen’s ambition was what finally broke it. That year Takeda Shingen negotiated a secret deal with Tokugawa Ieyasu (he had changed his name to this form in 1566, by petition to the Imperial Court) to divide the Imagawa domain between them. The Tokugawa would take Totomi, the Takeda would take Suruga. However, both men possessed great ambition and during the invasion Takeda troops attempted to conquer Totomi, and Ieyasu sheltered Ujizane after the latter agreed to cede his land to the Tokugawa.
At the same time, Hojo Ujiyasu was enraged by Shingen’s one-sided actions and launched an invasion of Suruga in an attempt to throw the Takeda out, commanded by Ujimasa. Shingen’s response was to attack Odawara Castle itself in 1569. However, the Takeda overextended, leaving Hojo castles to their rear intact, and were forced to leave after burning the castle town to the ground. During the retreat the Hojo attempted an ambush at Mimasetoge, fought off with heavy casualties to the Takeda. In 1570 Ujiyasu died, and Hojo Ujimasa maintained the war with the Shingen for another year before agreeing to peace. This effectively set the stage for the events of the next decade.
In conclusion by agreeing not to attack each other the Imagawa, Takeda, and Hojo made it possible for them to attend their ambitions without fear of destabilizing the Kanto. In the end, it all came up short. Imagawa Yoshimoto underestimated Oda Nobunaga and paid with his life, making the Oda ascendancy possible in the process. Both Takeda Shingen and Hojo Ujiyasu found themselves blocked by an enemy who proved to be their equal in Uesugi Kenshin, resulting in a bloody stalemate between all three. Ambition, which brought the alliance together, tore it apart.