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3rd day of the 1st month, Eiroku 7 (January 1564)
Kokufu-dai, Shimofusa Province (present-day Ichikawa City, Chiba Prefecture)
About 17 min read
The Second Battle of Kokufu-dai (Daini Kokufu-dai Kassen) took place on the 3rd of January, Eiroku 7 (1564) at Kokufu-dai in Shimofusa Province (present-day Ichikawa City, Chiba Prefecture), fought between the Later Hōjō and Satomi clans during the Sengoku period. The designation "Second" distinguishes this battle from an earlier engagement at the same location fought by Hōjō Ujitsuna and Satomi Yoshitaka on the 7th of Tembun (1538)—the First Battle of Kokufu-dai. This battle became a critical turning point in the Later Hōjō's conquest of the Kantō region, forcing the Satomi clan to retreat significantly. The Kokufu-dai plateau overlooked the Edo River and held high strategic value as a transportation hub connecting Musashi, Shimofusa, and Kazusa provinces.
In the mid-Sengoku period, the Kantō region witnessed shifting alliances among multiple powers: the Later Hōjō (of Sagami), the Satomi clan (Sengoku daimyo of Awa), Uesugi Kenshin (Kantō Deputy Shogun and lord of Echigo), and the Koga Kubo (the Ashikaga shogunal cadet line). In Eiroku 3 (1560), Uesugi Kenshin led a large army into the Kantō as "Kantō Deputy Shogun," and the following year (Eiroku 4, 1561) he laid siege to Odawara Castle (the Siege of Odawara Castle). At this time, Satomi Yoshihiro participated in Kenshin's Kantō campaign as a counterbalance to Later Hōjō power. However, Kenshin failed to subdue the Hōjō and withdrew to Echigo, leaving the Kantō daimyo to resume their intricate web of diplomatic and military maneuvering.
When Kenshin withdrew to Echigo, the Hōjō intensified their confrontation with the Satomi. Around Eiroku 5–6 (1562–63), Satomi Yoshihiro aggressively expanded eastward into Kazusa, extending Satomi influence near the Shimofusa-Kazusa border. Hōjō Ujiyasu and his son Ujimasa would not tolerate this expansion and resolved on a large-scale counteroffensive against the Satomi. While absorbing defectors from the Koga Kubo and the Yamanouchi Uesugi, the Hōjō worked to establish their hegemony across the entire Kantō.
On the morning and into midday of Eiroku 7, the 3rd of January (1564), both armies clashed across the Kokufu-dai plateau. Some accounts report that Satomi forces initially used the terrain to contain the Hōjō advance. However, since detailed primary sources are sparse, much of what is known about the battle's specifics comes from later military chronicles and local histories.
Under the command of Hōjō Ujiyasu and Ujimasa, the Hōjō forces drove the Satomi army to the brink and dealt it a devastating blow in fierce hand-to-hand combat. Masaki Nobushige, a prominent Satomi general, fell in battle. Nobushige was a valiant warrior who had succeeded to the name of his father Masaki Tokishige (called Yari Daizen), and his death was a severe blow to the Satomi clan. Yoshihiro barely managed to escape the battlefield and flee to Awa. This defeat cost the Satomi their strongholds in Kazusa and Shimofusa, forcing them into a defensive retreat to Awa Province (southern Boso Peninsula) for years to come.
Through this victory, Hōjō Ujiyasu solidified his control of Shimofusa and Kazusa and secured the Later Hōjō's hegemony over the Kantō. That same year, Ujiyasu maintained the "Kō-Sō-Sun Tripartite Alliance" with Takeda Shingen and Imagawa Ujizane while consolidating a stable regime of control over southern Kantō.
The Second Battle of Kokufu-dai, as a manifestation of the Later Hōjō's military ascendancy in eastern Japan during the Sengoku period, is deeply intertwined with the history of Japanese blades. The Hōjō, controlling the Sōshū tradition smithing centers around Sagami Province and Kamakura, inherited blades descended from the lineages of master smiths—Masamune, Sadamune, Hiromitsu, and Akihiro—whose works dominated the Sōshū tradition from the Kamakura era through the Muromachi and Sengoku periods. Such blades were transmitted among the Hōjō clan's samurai.
Hōjō Ujiyasu himself excelled not only in military strategy but also in statecraft, earning the reputation of a "diplomatic" Sengoku daimyo—a status recognized well into the early modern period. While no detailed records of his personal blades survive, his rule of Sagami Province, where Sōshū master smiths flourished, suggests he likely wore blades in the Sōshū tradition. Ujiyasu and Ujimasa maintained retainers charged with procuring and managing the clan's martial equipment, ensuring a steady supply of practical blades for battle. After major engagements, blades taken from the fallen were incorporated into the clan's arsenal and preserved as heirlooms—a practice common among all Sengoku daimyo, not merely the Hōjō.
Masaki Nobushige, who fell at this battle, is remembered as a valiant general who sustained the Satomi of Awa. The Masaki clan maintained close ties to smiths and metalworkers of Awa, making them indispensable to any account of the Boso Peninsula's blade culture. The location of Kokufu-dai, now within Ichikawa City, retains historical significance and transmits the memory of blades crossed in Sengoku conflict to the present day.
After the Second Battle of Kokufu-dai, the Satomi clan found itself on the defensive against the Hōjō for many years. Yet at the Battle of Mifuneyama in Eiroku 9 (1566), Satomi Yoshihiro defeated Hōjō forces and achieved a measure of recovery. The Sengoku-period history of the Kantō continued thereafter, with the Hōjō, Uesugi, Takeda, Satomi, and Satake clans remaining intricately intertwined. In Tenshō 18 (1590), Toyotomi Hideyoshi's Odawara Campaign marked the fall of the Later Hōjō, bringing an end to their Kantō dominion and initiating the epochal shift in Japanese history that led to Tokugawa Ieyasu's transfer to the Kantō. The Battle of Kokufu-dai stands as a quiet inscription at the intersection of history and the blade, a memory of the tumultuous era that shaped the samurai of eastern Japan.
The First Battle of Kokufu-dai (Tembun 7, 1538) saw Hōjō Ujitsuna defeat a coalition of the Ōgimarugata Uesugi and Satomi Yoshitaka, marking a turning point in the Later Hōjō's rise to dominance in southern Kantō. That the Second Battle of Kokufu-dai played out at the same location twenty-six years later demonstrates the consistency of the Hōjō's eastern strategy. Kokufu-dai was no mere coincidental battlefield but a deliberately chosen strategic strongpoint, recognized as a critical transportation and military hub in the Kantō.
The Later Hōjō's military organization stood out among Kantō daimyo for its systematic character. Their skill in domain administration, their favorable treatment of the peasantry, and the rationality of their castle construction were recognized hallmarks of Later Hōjō strength. From a blade perspective as well, the Hōjō controlled Sagami Province's smithing centers and patronized the heirs of the Sōshū tradition. Though Sōshū techniques declined through the Sengoku era, some smiths maintained their lineage under Later Hōjō protection.
The Satomi, based in Awa Province (present-day southern Chiba Prefecture), formed a distinct cultural sphere within the Boso Peninsula. As a maritime domain, Awa excelled in naval operations and absorbed cultural artifacts through coastal trade. Records of the Satomi's samurai bearing particular blades are fragmentary, yet local smiths in Awa forged blades for the Satomi warriors. The swords of Satomi braves, including Masaki Nobushige, gleamed on the Kokufu-dai battlefield, and many were subsequently scattered or lost.
When a warrior fell in battle, his blade often became a war trophy carried off by the victor. The fate of Masaki Nobushige's sword, which he bore when he fell at the Second Battle of Kokufu-dai, remains unknown, though it likely passed into the Later Hōjō's possession. Such shifts in ownership occasioned by combat create a complex history particular to Japanese sword transmission. When tracing the provenance of modern museum blades, one often discovers pathways marked by Sengoku battles, war spoils, and formal gift-giving. The Battle of Kokufu-dai, too, remains quietly inscribed in this distinctive history of blade provenance.
Twenty-six years after the Second Battle of Kokufu-dai, in Tenshō 18 (1590), Odawara Castle fell under siege by Toyotomi Hideyoshi's massive army, and the Later Hōjō were destroyed. The Odawara Campaign scattered a substantial portion of the wealth and blade collections that the Hōjō had accumulated. Hideyoshi confiscated the Later Hōjō's treasures and distributed portions as rewards to his generals. The Sōshū blades and renowned heirlooms amassed during the Hōjō's century of rule in Sagami were dispersed across the realm at this juncture. The Satomi, by contrast, submitted to Hideyoshi in the Odawara Campaign and were permitted to continue their rule in Awa Province. Through this survival, the Satomi's inherited blades remained in the family line into the Edo period. The swords borne by the Later Hōjō and Satomi clans when they clashed at Kokufu-dai found their fates again reshaped by history's currents twenty-six years later; each traversed a distinct path into the hands of posterity.