Yamanaka Castle

Connection to Swords

The sword culture of Yamanaka Castle and the Later Hōjō clan must be understood from their unique cultural position as a major daimyō family managing the Tōkaidō, Japan's most crucial transportation route. The Later Hōjō, ruling the Kantō region from their base in Sagami (Kanagawa), occupied a strategically vital frontier. The Tōkaidō route through the Hakone region, where Yamanaka Castle stood, formed a vital boundary line between the Imagawa clan, which controlled Suruga (Shizuoka), and the eastern domains that later fell under Tokugawa Ieyasu's rule. In the Later Hōjō's sword culture, the deepest and most essential element was their connection to Sōshū-den, the Sagami sword-forging tradition. Sōshū-den represents the supreme tradition of Japanese swordmaking, having produced the greatest master smiths of the Kamakura and Nanboku-chō periods—Masamune, Sadamune, Akihiro, and Hiromasa—and Sagami Province, which the Hōjō dominated, was the very birthplace of this tradition. Successive Later Hōjō lords—Hōjō Ujiyasu, Ujimasa, and Ujiteru—ruled the Sagami lands where descendants of Sōshū-den smiths remained, making them the samurai most directly blessed by this sword culture. The legendary stand of Mamiya Yasutoshi, the warrior commander who fought fiercely during Yamanaka Castle's fall, is remembered as a historical moment embodying both the spirituality of Hōjō samurai and this sword culture. The half-day battle of Yamanaka Castle represents the moment when Hōjō swords and mountain fortifications were overcome by Toyotomi firearms, spears, and numerical superiority—a vivid example of the transformation in warfare methods at the end of the Sengoku period. Yet the spirit of Hōjō samurai, who wielded swords until the very end, resonates with Sōshū-den's principle of "unbreakable and keenly sharp" combat blades. Today, the Mishima City Local Museum (within Rakujuen Park) displays the history, archaeological remains, and samurai culture of the Later Hōjō at Yamanaka Castle, exhibiting excavated artifacts—such as musket balls and ceramics—alongside period arms, armor, and sword-related materials. Yamanaka Castle ruins stand as a rare historical site where one can simultaneously enjoy both the spectacular vista of Mt. Fuji and the ingeniously designed shoji-bori—an essential destination for both sword enthusiasts and castle devotees alike.