The tantō appeared during the Heian Period (795-1192 A.D.) and developed as a weapon during the Kamakura Period (1192-1333 A.D.). At that time the tantō was not just a weapon but also a work of art. It was richly decorated using the most spread styles: hira-tsukuri and uchi-sori. Later, in the Nambokucho period (1336-1392 A.D), tantōs become longer than 15.75 inches (37 cm). Blades become thinner and broader and thus even more dangerous. Different styles developed and the shape changed. During the Muromachi Period (1336–1573 A.D.) the tantō becomes once more narrow-bladed.