A is a type of traditionally made Japanese sword (nihonto) worn by the samurai class of feudal Japan. Tachi and katana generally differ in length, degree of curvature, and how they were worn when sheathed, the latter depending on the location of the mei (銘), or signature, on the tang. The tachi style of swords preceded the development of the katana, which was not mentioned by name until near the end of the twelfth century. Tachi were the mainstream Japanese swords of the Kotō period between 900 and 1596. Even after the Muromachi period (1336–1573), when katana became the mainstream, tachi were often worn by high-ranking samurai. History The production of swords in Japan is divided into specific time periods: Jōkotō (ancient swords, until around 900) Kotō (old swords from around 900–1596) Shintō (new swords 1596–1780) Shinshintō (new new swords 1781–1876) Gendaitō (modern or contemporary swords 1876–present) The predecessor of the Japanese sword has been called warabitetō (:ja:蕨手刀). In the middle of the Heian period (794–1185), samurai improved on the warabitetō to develop kenukigata-tachi (:ja:毛抜形太刀) -early Japanese sword-. To be more precise, it is thought that the Emishi improved the warabitetō and developed Kenukigata-warabitetō (:ja:毛抜形蕨手刀) with a hole in the hilt and kenukigatatō (:ja:毛抜形刀) without decorations on the tip of the hilt, and the samurai developed kenukigata-tachi based on these swords. Kenukigata-tachi, which was developed in the first half of the 10th century, has a three-dimensional cross-sectional shape of an elongated pentagonal or hexagonal blade called shinogi-zukuri and a gently curved single-edged blade, typical features of Japanese swords. There is no wooden hilt attached to kenukigata-tachi, and the tang (nakago), integrated with the blade, is directly gripped and used. The term kenukigata is derived from the fact the central part of tang is hollowed in the shape of an ancient Japanese tweezers (kenuki). In the tachi developed after kenukigata-tachi, a structure in which the hilt is fixed to the tang (nakago) with a pin called mekugi was adopted. As a result, a sword with three basic external elements of Japanese swords, the cross-sectional shape of shinogi-zukuri, a gently curved single-edged blade, and the structure of nakago, was completed. Its shape may reflect the changing form of warfare in Japan. Cavalry were now the dominant fighting unit, and the older straight chokutō were unsuitable for fighting from horseback. The curved sword is a far more efficient weapon wielded by a warrior