承平・天慶の乱期

The Jōhei-Tengyō revolts (935–941) constituted the most severe political crisis of the Heian period, with Taira no Masakado's uprising in the east and Fujiwara no Sumitomo's piracy in the west erupting simultaneously. The imperial court, lacking its own military capacity, was forced to rely on warrior families for suppression. Fujiwara no Hidesato and Taira no Sadamori, who defeated Masakado, and Minamoto no Tsunemoto, who destroyed Sumitomo, became pioneers of the new warrior social class. From a sword history perspective, this era represents a critical transitional period when Japanese blades began shifting from the continental straight-sword (chokutō) toward curved forms. Early curved blades with curvature near the base were experimentally produced for use on horseback, setting the stage for the refined tachi of the Kamakura period. Taira no Masakado's rebellion turned the entire Kantō region into a battlefield, and the accumulated experience of mounted combat led to the recognition that curved swords were superior to straight ones for drawing and cutting from horseback. The social status of the sword was also transforming: swords began functioning not merely as weapons but as symbols of warrior prestige, given as rewards alongside land grants and official rank. The legendary smith Yasutsuna of Hōki (Inaba province) is considered the earliest named swordsmith, and his masterwork, the Dōjigiri Yasutsuna (National Treasure), stands as the singular surviving artifact conveying sword-craft standards of this dawn age. Physical survivals from this period are almost nonexistent, making archaeological and literary-historical approaches essential for understanding these formative decades.