YAMAGA SOKŌ (1622–1685), Japanese Confucian of the school of Ancient Learning (Kogaku). Sokō was born in Aizu, the son of a masterless warrior named Yamaga Sadamochi (1585–1664) and Sadamochi's mistress, Myōchi (d. 1677). He began studying the Confucian classics at the age of five or six, and at eight he was en rolled at the Hayashi school in Edo (present-day Tokyo). As a youth, he also studied Japanese literature, Shintō, and military science—the latter with Obata Kagenori (1572–1663) and Hōjō Ujinaga (1609–1670).

Sokō first achieved fame in 1642 when he published Heihō yūbishū (Collected Writings on Military Methods and Preparedness), a fifty-volume work on military science that treated a whole range of subjects from castle defense to warrior organization. Over the next two decades his lectures on military affairs and the Chinese classics attracted growing numbers of local warriors and lords. In 1652 Sokō entered...