Historically, katana (刀?) were one of the traditionally made Japanese swords (日本刀 nihontō?) that were worn by the samurai class of feudal Japan, also commonly referred to as a "samurai sword". Modern versions of the katana are sometimes made using non-traditional materials and methods.
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. It has historically been associated with the samurai of feudal Japan and has become renowned for its sharpness and strength.
During the Meiji period the samurai class was gradually disbanded and the special privileges granted to them were taken away including the right to carry swords in public.
The Haitōrei Edict in 1876 forbade the carrying of swords in public except for certain individuals, such as former samurai lords (daimyo), the military, and police. Skilled swordsmiths had trouble making a living during this period as Japan modernized its military and many swordsmiths started making other items such as farm equipment, tools, and cutlery.
Military action by Japan in China and Russia during the meiji period helped revive interest in swords but it was not until the Showa period that swords were produced on a large scale again. Japanese military swords produced between 1875 and 1945 are referred to as guntō (military swords).
During the pre World War II military buildup and throughout the war, all Japanese officers were required to wear a sword. Traditionally made swords were produced during this period, but in order to supply such large amounts of swords blacksmiths with little or no knowledge of traditional Japanese sword manufacture were recruited. In addition, supplies of the Japanese steel (tamahagane) used for sword making were limited, so several other types of steel were used, as well.
Short-cuts in forging were also taken, such as the use of power-hammers, and tempering the blade in oil, rather than hand forging and water tempering. These techniques generated swords without the various characteristics associated with "true" Japanese swords.
The non-traditionally made swords from this period are called "showato" after the regnal name of the Emperor Hirohito, and in 1937, the Japanese government started requiring the use of special stamps on the tang (nakago) to distinguish these swords from traditionally made swords.
During this period of war, older antique swords were remounted for use in military mounts. Presently, in Japan, showato are not considered to be "true" Japanese swords and they can be confiscated. Outside of Japan, however, they are collected as historical artifacts.