Establishment of Sagami-den

Kamakura Shogunate and Sagami Province's Sword Environment

During the Kamakura period (1185–1333), Sagami Province (present-day Kamakura, Kanagawa Prefecture) served as the center of Japan's political and military power. Skilled warriors and craftsmen from across the nation gathered at this location, creating heightened demand for swords that were both practical in combat and artistically distinguished. Eminent sword smiths were recruited from Yamato Province and Bizen Province. This cultural and technical exchange formed the foundation for the emergence of the Sagami-den.

Shintōgo Kunimitsu and the Genesis of the Sagami-den

The progenitor of the Sagami-den is regarded to be "Shintōgo Kunimitsu." Active during the mid-Kamakura period (late 13th century), Kunimitsu built upon the techniques of the Yamato tradition (originating in Nara) while pursuing an independent technical direction within Kamakura. Notably, in the forging of the steel structure (ji-tetsu) and the composition of the hamon, he demonstrated an orientation distinct from the earlier Yamato and Bizen traditions. Though his blades are scarce in number, they are highly regarded as a seminal point for the technical innovations that would flow through to Masamune and Sadamune.

Masamune and His Revolutionary Techniques

The figure who brought the Sagami-den to world recognition is "Okazaki Masamune." Active during the late Kamakura period to the early Northern and Southern Courts period (late 13th century to early 14th century), Masamune effected revolutionary changes across all three elements of sword craft: the steel structure (ji-tetsu), the hamon, and the form (sugata).

Masamune's greatest technical innovation lies in the pinnacle of "nie-deki" (coarse nie emergence). In contrast to the earlier Bizen tradition's expertise in "nioi-deki"—a fine, continuous pattern of nie particles appearing as a scent—Masamune realized a hamon of dramatic "ō-nie" (coarse nie), where large, coarse nie particles ignite and surge violently. This hamon, intensely undulating from the ha-machi near the blade edge toward the kissaki (tip), displays abundant activity: yu-bashiri (vapor trails), kin-suji (golden lines), inazuma (lightning streaks), and sunagashi (sand flows). The steel structure, too, shows large ō-itame (large wood-grain pattern) uniformly covered by large particles of ji-nie, presenting a deep, lustrous black-tinted iron of great refinement.

Regarding form, the blade exhibits shallow curvature and an enlarged kissaki, which presaged the transition to the "Enno-Teiji tachi" form of the Northern and Southern Courts period.

Sadamune and the Refinement of the Sagami-den

"Sadamune," a disciple of Masamune, moderated the intense coarse nie-deki of his teacher somewhat while establishing a more precise, refined variant of the Sagami-den tradition. Sadamune's blades are also called the "gentler Sagami-den," and while lacking the intensity of Masamune's work, they attain the pinnacle in the beauty of the steel structure and the richness of the hamon's activity. In the Edo period, an evaluation emerged that called "Masamune, Gō Yoshihiro, and Awataguchi Yoshimitsu" the "Tenka san-sa" (Three Great Masters of the Realm).

The Technical Legacy of the Sagami-den

The establishment of the Sagami-den exerted far-ranging influence on the subsequent history of the Japanese sword. From the Muromachi through the early Edo period, sword smiths from all provinces—Bizen, Mino, Yamato, Echizen, and others—incorporated the techniques of the Sagami-den and attempted "Sagami-den utsushi" (Sagami-den imitations). Particularly in the late-koto period, smiths such as Kanemoto and Kanesada of Mino, and in the shinto period, smiths of Echizen and Hizen, left numerous blades showing conscious emulation of Masamune's coarse nie-deki. The name "Masamune," known globally as "Masamune," became synonymous with the Japanese sword itself.