Kōnin-Jōgan Period — The Dawn of the Classical Japanese Sword

Historical Background of the Kōnin–Jōgan Period

The Kōnin and Jōgan eras (810–877) corresponded to the reigns of Emperor Saga and Emperor Seiwa, a transitional phase from the stable to the changing period of the ritsuryō system. In this era, the court began responding to the need for practical weapons as regional clans rose to power. As diplomacy with Tang China shrank and the Japanese missions to Tang China moved toward abolition (the last was in 838), this was also the budding stage of the kokufū culture, in which uniquely Japanese culture flowered across many fields.

In swordmaking, the Emishi and fushū (subjugated Emishi) of the Tōhoku region modified the warabite-tō, angling the hilt and giving the blade a curve to increase its effectiveness. These improvements are thought to have led to the later curved swords (wantō).

Technical Transition Toward Old Swords

The Sohaya, a great sword at Kiyomizu-dera (Katō, Hyōgo Prefecture) that is traditionally said to have been carried by Sakanoue no Tamuramaro, has a shallow curve along its entire blade. It is also considered an early example of the process by which straight swords changed into curved swords from the late Nara period to the mid-Heian period. Afterward, the curvature increased through the kenukigata-tō and kenukigata tachi, and it is generally thought that the tachi shifted to curved blades after the mid-Heian period.

Battles with the Emishi and Swords

Through the wars of conquest against the Emishi (including the Thirty-Eight Years' War), demand grew for excellent weapons that could be used effectively in combat, and improving sword quality became an urgent task. Sakanoue no Tamuramaro (758–811), a warrior of the conquest campaigns, died at the beginning of this period.

Legacy for Later Generations

The shift from straight swords to curved swords that advanced during the Kōnin and Jōgan periods led to the formation of the tachi after the mid-Heian period. Yasutsuna of Hōki and Sanjō Munechika of Yamashiro, the earliest smiths with extant signed works, are thought to have lived around the late 10th century.