南北朝

The Nanbokuchō period saw Japan split between two imperial courts, unleashing fierce battles nationwide. As warfare shifted from mounted combat to infantry, enormous swords called ōdachi and nodachi—with blades over three shaku (90 cm)—became prevalent. These grand weapons featured wide blades, thick kasane, and powerful proportions that retained impressive dimensions even when later shortened. Smiths of the Sōshū tradition produced flamboyant hamon with hitatsura (full-temper) and nie-based patterns, while Bizen masters like Kanemitsu and Chōgi excelled at vigorous gunome-midare. The Yamato tradition continued through the Taima and Tegai schools serving temple commissions, while Nobukuni carried on the Yamashiro tradition in Kyoto. Southern Court warriors such as Kusunoki Masashige and Kitabatake Akiie were recorded wielding ōdachi, making these weapons symbols of martial valor. The distinctive proportions of this era, known as 'Nanbokuchō-taihei,' profoundly influenced later generations. Most surviving ōdachi have been shortened into katana, making unaltered examples museum-level treasures. Because many naginata and tachi from this period were later altered, numerous unsigned masterworks bearing Nanbokuchō-era steel also exist.