Three old swords and one modern sword were examined critically for chemical composition and metal structure. The old blades were composed of steel of several different compositions interwoven by repeated forging, then heat treated in a manner to produce a controlled gradient of hardness and finished by a method that gives surfaces of geometric precision displaying surface patterns of subtle texture which depends on the underlying metallographic features. The sword owes its efficacy to an extremely hard martensitic edge backed by a somewhat heavy and relatively soft body. Forging technique, grain structure, the hardened zone (called <i>yakiba), and the body of the blade are discussed in detail and amply described with help of 47 illustrations including metallographs and diagrams. -- AATA