Japanese sword forging craft

Timeline

1. c. 1400–1500Bizen Province · BizenIn the 15th century, swordsmiths in Bizen, Yamashiro and elsewhere produced tamahagane with tatara furnaces, repeatedly folding and hammering to remove impurities and adjust carbon content; combined with jacket-steel techniques (kofuku-uchi, kissaki-tsukuri), this produced blades soft outside and tough within, laying the foundation for large-scale sword use in the Warring States period.
2. 1571–1580Seki, Mino Province · SekiAs Oda Nobunaga unified Kinki and the Tōkaidō in the 1570s, he ordered large quantities of tachi and wakizashi to equip ashigaru and cavalry; smiths in Seki (Mino), Bizen and elsewhere expanded production to meet wartime needs, standardizing quenching and polishing, with blade curvature and kissaki shapes suited to mounted and foot combat.
3. 1575–1582Kyoto · KyotoIn the later 1570s, fine Japanese swords served not only on the battlefield but also as honors bestowed by daimyō on retainers; inscriptions of smith names, jihada and hamon (such as the three generations of Bizen, Seki Magoroku) became key criteria for identifying schools and status, driving smithing toward refinement and branding.