Kenjutsu Schools and Sword Evolution

The shape of the Japanese sword was not determined solely by the smith's aesthetic sense and the properties of the materials used. The techniques and theories established by kenjutsu schools — the predecessors of modern kendō — directly influenced blade design. When a school founder or headmaster judged that "executing this technique to its fullest requires a blade of this particular form," the smith would create a blade in response to that demand. The relationship between kenjutsu schools and sword makers transcended a simple customer-craftsman relationship; it was a shared creative endeavor of philosophy and technique.

From the late Muromachi period through the Sengoku era, the systematization of kenjutsu progressed rapidly. Early schools — Nen-ryū, Kage-ryū, Tomita-ryū — formed and became the sources of later major traditions. Blades of this era, reflecting the realities of Sengoku warfare, tended to be comparatively long (blade length of approximately 2 shaku 4 sun to 2 shaku 8 sun) and were designed with purely practical intent. Among schools, philosophical debates arose regarding the "length" of blades: Kamiizumi Nobutsuna (Shinkage-ryū) emphasized longer swords, while Tsukahara Bokuden (Kashima Shintō-ryū) advocated flexible adaptation to circumstances.

The systematization of Ittō-ryū (Itō Ittōsai → Ono Tadaaki) was completed in the early Edo period, placing "kiriotoshi" — the doctrine of the decisive cutting stroke — at its philosophical center, and it taught that the balance of blade length, weight, and curvature directly determined the execution of technique. Practitioners of Ittō-ryū commissioned sword makers to forge blades of specific dimensions and forms, and swords made to Ittō-ryū specifications came to be recognized as a distinct category. Conversely, Jigen-ryū (Satsuma), with its distinctive "dragonfly stance" that wagered everything on a single initial strike, favored thick, sturdy blades with the balance point shifted toward the hilt. This preference resulted in the characteristic, practical, and imposing nature of Satsuma blades.

Shinkage-ryū (the Yagyū clan), serving as the military instructors of the Edo shōgunate, exerted tremendous influence on sword culture as a whole. The blade ideal envisioned by the Yagyū clan was one capable of enduring both training and actual combat — a "practical equilibrium" — and this became one of the standard design principles for blades in the early Edo period. Furthermore, the development of iaijutsu (such as Lin-崎 Musō-ryū) promoted research into the curvature and inner curvature of blades to maximize drawing speed (sayabanashiri), adding a new dimension to blade design considerations.

By the Bakumatsu era, many schools including Hokushin Ittō-ryū (Chiba Shūsaku) and Kagami Shinmeii-ryū conducted practical training at their dōjō, and with the spread of training methods centered on bamboo and wooden swords, the demand for actual blade designs also became more diverse. Hokushin Ittō-ryū, in which Sakamoto Ryōma trained at the Chiba dōjō, was known for emphasizing practical and mobile techniques. The demands of schools and the craftsmanship of sword makers continued to influence each other until the very end, and with the decline of swordsmanship brought about by the Sword Abolition Edict (1876), this rich era of dialogue drew to a close.