The Historical Masamune
The historical Masamune's familiar name is Goro Nyudo. Masamune is probably the best known Japanese swordsmith of all time, as well as a well-known philosopher.
Masamune is believed to have worked in Sagami Province during the last part of the
Kamakura Era (1185-1332), and it is thought that he was trained by swordsmiths from Bizen and Yamashiro provinces, such as Kunitsuna and Kunimitsu.
The first famous swordsmith active in Kamakura, Sagami province was Shintogo Kunimitsu. It is claimed (in Kanchiinbon Meizukushi) that he was a grandson of a swordsmith of the Taima school in Yamato province. It is generally accepted that Kunimitsu had two pupils, Yukimitsu and Masamune. The earliest among Kunimitsu's works are those reliably dated to 1293 and the latest dated 1324. Judging from the dates of Kunimitsu's works, Masamune was active from the end of Kamakura (1185-1332) to the very early years of the Nanbokucho (1333-1391) period.
The Soshu School:
Masamune is credited with creating the Soshu tradition of swordmaking during his career. "Soshu" or Soshu Kitae as it is formally known, is a seven layer lamination technique used in making the blade. The heart of the blade is formed from softer, more malleable steel giving it exceptional flexibility. There is then a layer of slightly harder steel bonded to each side of the blades heart, giving it support. The last layers are a very hard steel bonded to the top, bottom, and both sides of the core forming the ha (cutting edge) mune (back edge) and shinogi-ji (blade flats). This form of laminar construction provided for a sword that could be sharpened to a razor edge due to the hardened steed used for the ha, but was extremely resilient to battle damage due to its softer more flexible core. Masamune's adopted son, Sadamune succeeded him as master of the Soshu tradition.
In addition, legend has it that there were "10 Disciples of Masamune," or ten swordsmiths that continued working in Masamune's Soshu tradition of sword making, and that several already well-known swordsmiths also came to study with Masamune. The Masamune Jittetsu, as these smiths were called, worked in their own tradition as well as studying the techniques of Masamune.
Regardless of whether or not this is a historical fact, the swordsmiths working at the end of the Kamakura to the Nanbokucho periods produced works with the surface texture featuring nie, a distinguishing feature of the Masamune style. Nie are areas of bright crystalline structure in the hamon (temper-line) or ji (the blade surface between the ridgeline of the blade and the hamon), resulting from the interaction of the steel during the quenching process. Masamune's style is often referred to as "the beauty of nie," putting his blades in distinct contrast with Bizen blades.
Masamune's school of swordmaking is also often characterized by the soft, flowing hamon visible on his blades. A proper polish is required for the activities in the hamon to be well visualized. (An active hamon is normally the mark of a better quality blade.)
Documented Swords:
Masamune created many superb swords, and all of his surviving blades are considered national treasures in Japan. Seeing his signature on a sword is extremely rare, and there are just a few swords authenticated as his work. This body of work includes a few unsigned swords attributed to him. Their splendid craftsmanship has led to the high praise of Masamune as a master swordsmith. "Fudo Masamune," "Kyogoku Masamune," and "Daikoku Masamune" are accepted examples of his genuine works.
Masamune's works are the most frequently cited among the swords listed in the Kyoho Meibutsu Cho, a catalogue of "excellent swords" in the collections of daimyos edited during the Kyoho era (1716-1736) by Hon-ami.
Today, the name Masamune has become synonymous with "an excellent sword".
information and references used for this post include works by Jinsoo Kim (Nihon-to Books) and The Japanese sword guide, found at