Tachi A was a type of Japanese sword worn by the samurai class of feudal Japan . The tachi style of swords preceded the development of the katana . History and description . The production of swords in Japan is divided into specific time periods ; Jokoto ( Ancient swords , until around 900 A . D . ) , koto ( old swords from around 900 - 1596 ) , shinto ( new swords 1596 - 1780 ) , shinshinto ( new new swords 1781 - 1876 ) , gendaito ( modern swords 1876 - 1945 ) . and shinsakuto ( newly made swords 1953 – present ) . Authentic tachi were forged during the middle ages , before 1596 . With a few exceptions katana and " tachi " can be distinguished from each other if signed , by the location of the signature ( " mei " ) on the tang ( " nakago " ) . In general the " mei " should be carved into the side of the " nakago " that would face outward when the sword was worn . Since a " tachi " was worn cutting edge down , and the " katana " was worn cutting edge up the " mei " would be in opposite locations on the " nakago " of both types of swords . An authentic tachi that was manufactured in the correct time period averaged 70 – 80 centimeters ( 27 9 / 16 - 31 1 / 2 inches ) in cutting edge length ( " nagasa " ) and compared to a katana was generally lighter in weight in proportion to its length , had a greater taper from hilt to point , was more curved with a smaller point area . Unlike the traditional manner of wearing the katana , the tachi was worn hung from the belt with the cutting - edge down , and was most effective when used by cavalry . Deviations from the average length of tachi have the prefixes " ko - " for " short " and " ō - " for " great or large " attached . For instance , tachi that were " shōtō " and closer in size to a " wakizashi " were called " kodachi " . The longest tachi ( considered a 15th century " ōdachi " ) in existence is more than 3 . 7 meters in total length ( 2 . 2m blade ) but believed to be ceremonial . In the late 1500s and early 1600s many old surviving tachi blades were converted into katana by having their original tangs cut ( " o - suriage " ) , the signature ( mei ) would be lost in this process . For a sword to be worn in " tachi style " it needed to be mounted in a " tachi koshirae " . The tachi koshirae had two hangers ( ashi ) which allowed the tachi to be worn in a horizontal position with the cutting edge down . A sword not mounted in a tachi koshirae could be worn tachi style by use of a " koshiate " , a leather device which would allow any sword to be worn in the tachi style . Use . According to author Karl F . Friday , before the 13th century there are no written references or drawings etc that show swords of any kind were actually used while on horseback . The " uchigatana " was derived from the tachi and was the predecessor to the katana as the battle - blade of feudal Japan ' s " bushi " ( warrior class ) , and as it evolved into the later design , the tachi and the uchigatana were often differentiated from each other only by how they were worn , the fittings for the blades , and the location of the signature ( mei ) . As a result of the first Mongol invasion ( 1274 ) tachi started to be made thicker and wider . In later Japanese feudal history , during the Sengoku and Edo periods , certain high - ranking warriors of what became the ruling class would wear their sword tachi - style ( edge - downward ) , rather than with the saya ( scabbard ) thrust through the belt with the edge upward . With the rising of militarism during the Shōwa era , the Imperial Japanese Army and the Imperial Japanese Navy implemented swords called Shin guntō and Kai guntō which were worn tachi style ( cutting edge down ) .