In 1208 (Jōgen 2), Retired Emperor Gotoba summoned outstanding swordsmiths from across Japan to his detached palace at Minase and established the Gobankaji system, under which they took turns forging blades on a monthly rotation. Twelve master smiths from Bizen, Bitchū, and Yamashiro were chosen, and the Retired Emperor himself also hardened the edges of blades (the Kiku Gosaku). The system raised the Japanese sword beyond a weapon into a work of art and gave rise to the golden age of swords in the mid-Kamakura period. As a court-led policy to promote sword culture that set the precedent for later rulers' patronage of swordsmiths, it is counted among the most important cultural policies in the history of the Japanese sword.

KamakuraCultural Event

Kenchō era (1249–1256)

Establishment of the Sōshū Tradition — Shintōgo Kunimitsu and the Innovation of Kamakura Sword Culture

In the Kenchō era (1249–1256), at the invitation of Hōjō Tokiyori, regent of the Kamakura shogunate, Awataguchi Kunitsuna moved from Yamashiro to Kamakura. Shintōgo Kunimitsu, said to be his son or adopted son, established the foundation of the Sōshū-den in the late Kamakura period, based on techniques that took root in Sōshū (Sagami Province, present-day Kanagawa Prefecture). Kunimitsu drew on the techniques of the Yamashiro-den (Awataguchi) and Bizen-den, creating a new style built on suguha with strong nie and visible kinsuji and inazuma activity. This technique was passed on to his disciples Yukimitsu and Masamune and completed as the Sōshū-den, characterized by ara-nie-deki hamon.

KamakuraCultural Event

c. Hōji–Kenchō eras (1247–1256)

Establishment of the Bizen Osafune School — Mitsutada and the Apex of Bizen Sword Culture

In the mid-Kamakura period (according to ancient records, around the Hōji and Kenchō eras, 1247–1256), Mitsutada forged swords in Osafune, Bizen Province (present-day Osafune-chō, Setouchi City, Okayama Prefecture), establishing the foundation of the Bizen Osafune school. Inheriting the technical legacy of the Fukuoka Ichimonji school, which had flourished under the Goban-kaji system of Retired Emperor Go-Toba (1208), the school developed its own style by drawing on the geographic advantages of the Yoshii River basin and abundant iron sand (satetsu). Passed down through three generations, from Mitsutada to his son Nagamitsu and grandson Kagemitsu, the Osafune school became Japan's largest sword-producing center from the Kamakura through the Muromachi period, and many prominent warlords favored Osafune blades.