Japanese Sword Forging System

Timeline

1. 1200–1400Bizen Province · BizenSmiths smelted low-phosphorus tamahagane in a bellows-blown furnace, folding and hammering it over a dozen times to remove impurities and even out carbon content; the laminated construction method combined a hard steel edge with a soft iron core, laying the foundation for the distinctive cross-section and toughness of later Japanese swords.
2. 1580–1590Mino and Harima swordsmith centers · HarimaDuring the unification wars of Oda Nobunaga and Toyotomi Hideyoshi, daimyo placed large orders for swords to reward retainers; schools in Mino Seki and Bizen Osafune mass-produced katana and tachi in the 1580s, with quench-bending and hamon techniques reaching full maturity.
3. c. 1582–1600Kyoto–Osaka · KansaiBy the late 1580s, swordsmiths were graded by school and signature; Kyoto appraisal traditions influenced sword value. The Toyotomi regime controlled key swordsmiths, and swords served as battlefield weapons as well as symbols of power and diplomatic gifts.