Historically, katana (刀) were one of the traditionally made Japanese swords (日本刀 nihontō?) that were used by the samurai of ancient and feudal Japan. The katana is characterized by its distinctive appearance: a curved, slender, single-edged blade with a circular or squared guard and long grip to accommodate two hands.
The first use of “katana” (gatana) as a word to describe a long sword that was different from a tachi occurs as early as the Kamakura Period (1185–1333). These references to “uchigatana” and “tsubagatana” seem to indicate a different style of sword, possibly a less costly sword for lower-ranking warriors. The evolution of the tachi into the katana seems to have started during the early Muromachi period (1337 to 1573). Starting around the year 1400, long swords signed with the “katana” signature were made. This was in response to samurai wearing their tachi in what is now called “katana style” (cutting edge up). Japanese swords are traditionally worn with the signature facing away from the wearer. When a tachi was worn in the style of a katana, with the cutting edge up, the tachi’s signature would be facing the wrong way. The fact that swordsmiths started signing swords with a katana signature shows that some samurai of that time period had started wearing their swords in a different manner.
The rise in popularity of katana amongst samurai came about due to the changing nature of close-combat warfare. The quicker draw of the sword was well suited to combat where victory depended heavily on fast response times. The katana further facilitated this by being worn thrust through a belt-like sash (obi) with the sharpened edge facing up. Ideally, samurai could draw the sword and strike the enemy in a single motion. Previously, the curved tachi had been worn with the edge of the blade facing down and suspended from a belt.
The length of the katana blade varied considerably during the course of its history. In the late 14th and early 15th centuries, katana blades tended to have lengths between 70 and 73 cm (27½ and 28½ in). During the early 16th century, the average length approached closer to 60 cm (23½ in). By the late 16th century, the average length returned to approximately 73 cm (28½ in).