源平合戦期

The Genpei War (Jishō-Juei War, 1180–1185) was the pivotal five-year conflict between the Minamoto and Taira clans that ended in Taira destruction at the naval battle of Dan-no-Ura and inaugurated the Kamakura period of warrior governance. The war's scale and duration created unprecedented demand for battle-tested tachi throughout Japan. The major battles—Fujigawa (1180), Kurikara Pass (1183), Ichi-no-Tani, Yashima, and Dan-no-Ura (1184–85)—required vast quantities of reliable blades, driving smiths in Yamashiro, Yamato, and Bizen to expand production while maintaining quality. The Ichimonji school in Bizen was already producing distinctive chōji-midare hamon blades that would become synonymous with mid-Kamakura magnificence. Famous swords from this era—Kogarasumaru (associated with the Taira), Hizamaru and Higekiri (Minamoto treasures)—became legendary artifacts blending history and myth. The loss of the sacred sword Kusanagi-no-Tsurugi when the Taira's child-emperor Antoku drowned at Dan-no-Ura permanently fused the concepts of divine sword, imperial authority, and warrior tragedy in Japanese cultural consciousness. Warriors' experience of actual combat consolidated the belief that exceptional swords possessed spiritual power, accelerating the transition from sword-as-tool to sword-as-soul that would define Japanese sword culture for eight subsequent centuries.