Bun'ei Era

Bun'ei lasted from 1264 to 1275, under Emperors Kameyama and Go-Uda, shoguns Prince Munetaka and Prince Koreyasu, and the regents Hojo Masamura and, from 1268, Hojo Tokimune. In the tenth month of 1274, a combined Mongol-Goryeo force reached Hakata Bay via Tsushima and Iki (the Bun'ei Campaign). Kamakura retainers met unfamiliar tactics and weapons, which is thought to have sharpened interest in how their arms performed.

In swordmaking, Osafune Nagamitsu of Bizen developed bold, flamboyant choji-midare, while Rai Kuniyuki and Rai Kunitoshi of Yamashiro established a refined style of tightly knit small itame steel with suguha temper. Temple smiths of Yamato, such as the Tegai school, kept a sturdy, practical tradition. These styles gained their standing in the mid-to-late Kamakura period, and Bun'ei marks their maturity.

Socially, the shogunate organized guard duty against foreign attack (igoku keigo banyaku) along the Kyushu coast, increasing the military burden on warriors. Preparing for the second invasion in 1281 raised demand for, and expectations of, quality arms. Swords of the Bun'ei period reflect both the tension of Kamakura warrior society around the Mongol invasions and the maturing of Kamakura sword craft.