藤原摂関期

The Fujiwara Regency period (late 9th to late 11th century) witnessed the most fundamental transformation in Japanese sword history: the transition from straight blades (chokutō) inherited from the continent to the curved tachi that would define the Japanese sword for centuries. As mounted cavalry warfare became dominant, the functional advantages of a curved blade—greater cutting efficiency on the downstroke and faster draw—became apparent. Early curved swords show pronounced koshi-zori (curvature near the base), slender profiles, and small ko-kissaki points that reflect the aesthetic refinement of Heian court culture. Court nobles commissioned elaborate tachi fitted with gold-lacquered scabbards and braided silk cords, elevating sword production to a courtly art. The great temple-shrine complexes of Nara also drove demand as they organized armed monk-soldier (sōhei) forces, fostering the Yamato smithing tradition. In eastern Japan, independent warrior bands developed in regions beyond Fujiwara reach, as dramatized by the Taira no Masakado Rebellion of 939. Bizen province began its rise as a swordmaking center in this period, laying the groundwork for its later dominance. Surviving examples are counted in dozens worldwide, nearly all designated National Treasures, making them among the rarest and most historically significant artifacts in Japanese material culture.