Japanese swordsmiths achieved early technical mastery of steel-making and swords of excellent quality were made during the 8th century. Even the earliest examples featured a densely forged laminated structure of as many as 10,000 layers alternating in higher and lower carbon content hammered to exceptional toughness. The cutting edge of the Japanese sword has a crystalline structure, and since this is locked into a tough yet somewhat softer body, the sword has considerable flexibility.

Early Japanese furnaces were small and did not allow the total removal of slag as did the larger, more powerful tatara furnaces of the mid-18th century. But the existence of traces of slag, along with the intensive process of hammering and repeated folding and welding of the steel gave Japanese swords one of their unique qualities-a texture like wood grain, resulting from the small extrusions of slag beaten down to extremely fine layers.

The final stage in sword making was tempering and polishing, both done with techniques unique to Japan, and resulting in an accentuation of wave-like patterns known as hamon (temper patterns) on the sword's surface. One of the most beautiful features of a Japanese sword, the hamon also allow connoisseurs to identify a sword's origin. Each of the 200 or so schools of swordsmith-artists in Japan had identifiable blade characteristics. File marks (yasurime) on the tang (nakago) of the blade, the shape, and style of finishing, texture, tempering and color of steel are all taken into consideration in establishing the provenance of a sword. The signature of the smith is also often chiseled onto the tang.

While high-quality sword-making goes back to the 8th century, the golden age of the swordsmith in Japan was from 1050 to 1400. The history of swordmaking can be roughly divided into the Koto (Old Sword) period, from the 10th to the end of the 16th century and Shinto (New Sword) period (17th century onwards), when provincial lords (daimyo) encouraged a

revival of the sword art. Blades of the new period are generally regarded to lack the grace of earlier swords, but many had exquisite temper patterns. In addition to the katana and tachi swords used by warriors, sword connoisseurship also encompasses wakizashi blades, spears (yari), and halberds (naginata), as well as the sword guards (tsuba) and metal fittings for swords.

Japanese armor was flamboyant as well as functional. The o-yoroi style of armor employed from the 9th to 14th centuries was designed for combat on horseback and consisted of numerous flexible segments joined by richly colored cords. An iron helmet topped the armor, with tall stylized horns (kuwagata). Lavishly decorated saddles, bows and arrows, and miscellaneous weapons and colorful banners completed the warriors's inventory. The style and colors of the warrior's accouterments were designed to proclaim to the enemy the proud identity of his clan. By the 14th century, lighter types of armor (domaru) gradually replaced the o-yoroi. The introductions of firearms in the 16th century necessitated the development of a new style of armor (tosei gusoku).