Traditional Japanese katanas are famed for their incredible strength and cutting ability. Methods of making and perfecting these blades were developed in Japan as early as the 5th century. Steel-producing techniques were brought over from China and Korea, while the iconic curve of the swords is thought to have been influenced by Arabic-style weapons. There were several key periods in the history of Japanese sword production, including Jōkotō (ancient swords) and Shinshinto (new swords).
Using native Japanese steel, called Tamahagane, swordsmiths were able to gradually refine and purify the make-up of the blade by repeatedly folding the metal up to a dozen times. This is where the finished swords got their immense strength, which would be tested numerous times to ensure the steel contained no imperfections. The making of these swords declined during the 19th century as Japan steadily turned away from its samurai past and embraced Western culture, where guns, rather than swords, became the weapons of choice.
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