平安〜鎌倉

In the late Heian period, the transition from straight swords to curved blades gave birth to the Japanese sword as we know it. The Sanjō and Awataguchi schools in Kyoto established the Yamashiro tradition, known for refined and elegant workmanship. With the rise of the Kamakura shogunate, demand for battle-ready tachi surged, leading to the establishment of the Five Traditions (Gokaden): Yamashiro, Yamato, Bizen, Sōshū, and Mino. The mid-Kamakura period is regarded as the golden age of Japanese swordmaking, producing legendary smiths such as Masamune, Yoshimitsu, and Yoshihiro—the Three Greatest Smiths. The fusion of superb steel forging, beautiful hamon patterns, and functional curvature set the standard for all subsequent generations. Heian-era tachi are characteristically slender with deep koshi-zori (curvature near the base) and small ko-kissaki tips, reflecting the elegance of court culture. In the early Kamakura period, wider blades with ikubi-kissaki (stubby tips) appeared, and after the Mongol invasions (1274 and 1281), late Kamakura blades became broader with extended kissaki, evolving into imposing, powerful forms. Each of the Five Traditions cultivated its own forging methods and aesthetics: Yamashiro's refinement, Yamato's practicality, Bizen's flamboyance, Sōshū's boldness, and Mino's battlefield readiness. Swords from this era survive in limited numbers, and many are designated National Treasures or Important Cultural Properties, making them the pinnacle of collecting.