Obata Kagenori

Obata Kagenori (1572-1663) was a warrior and military scholar who flourished from the end of the Sengoku period into the early Edo period, leaving his name in the history of Japanese military science as the founder of the "Kōshū School of Military Science" (Kōshū Gungaku / Kōshū Military Science). Born as the son of Obata Masamori, a former retainer of Takeda Shingen, he systematized Takeda-style military law and tactics and widely transmitted them to the Edo shogunate and various daimyō.

Kagenori was born into a family of former Takeda Shingen retainers and was thoroughly trained in Takeda-style military law from his childhood. Even after the fall of the Takeda clan (1582), he retained his military knowledge and Takeda-style military science. Subsequently serving successive rulers—Toyotomi Hideyoshi, Tokugawa Ieyasu, and Tokugawa Hidetada—he refined and systematized Takeda military science. At the Battle of Sekigahara (1600), he was aligned with the Eastern Army (Tokugawa forces), and during the Siege of Osaka he distinguished himself through his service to the Tokugawa faction.

The Kōshū School of Military Science that Kagenori founded was systematized on the basis of Takeda Shingen's tactics, formations, and military science, supplemented with Confucian ethics and Eastern military theory. Through writings such as the "Kōyō Gunkan," Kagenori's Kōshū School of Military Science was widely read by Edo-period warriors and greatly contributed to the spread of Takeda-style military science. His disciple Hōjō Ujinaga brought the Hōjō School to fruition, and it was counted alongside the Kōshū School as one of the two major schools of military science in the Edo period.

In the realm of Japanese swords, Kagenori also contributed to the theoretical systematization of Takeda-style swordsmanship. In the Kōshū School of Military Science, swords were positioned not merely as weapons but as symbols of warrior spirituality and etiquette, and Kagenori's writings contain detailed descriptions ranging from sword selection and carrying to maintenance. As a warrior with real combat experience, Kagenori himself handled many blades and passed down to later generations the characteristics of swords used by Takeda-style warriors. Living beyond ninety years of age, Kagenori exerted tremendous influence on early Edo-period warriors as the last narrator of Takeda-style bushido and sword culture.