Japan’s early modern period (1568-1868) achieved a break from the violent political and social upheaval of the preceding Warring States period (1467-1568). The return to a stable and more centralized rule was made possible by the development and implementation of an emerging politico-religious trend, in which powerful leaders were posthumously apotheosized and worshiped as tutelary deities. Ieyasu, the first of the Tokugawa shoguns, was deified and venerated at the Tōshōgū Shrine in Nikkō, and the politico-religious movement that was propagated by Ieyasu’s descendants became a central tool for the government’s legitimacy. Because Ieyasu’s cult was the only source of ideological legitimacy that was exclusive to the Tokugawa, the sources of Tokugawa success can be found by examining the development of the Nikkō shrine and its accompanying religious movement.