Existing literature on peacebuilding arguably pays too much attention to host societies and not enough to the peacebuilders themselves. This article shows that, in many ways, Japan's contemporary approach to peacebuilding is the outward projection of its own postwar reconstruction experience. That experience constitutes a case of (re)building a postwar society by a transitional authority maintained by foreign intervention. In this process, the United States earned lasting and wide-ranging respect from many postwar Japanese citizens. It acted as a competent autocrat who effectively controlled information, imposed a strictly hierarchical order, tamed civil society, contained the seeds of postwar social disturbances, and paved the way for Japan's miraculous postwar growth. Within this framework, Japan successfully reconstructed the war-torn nation without local ownership, widespread democratic participation, or civil society involvement. This postwar experience profoundly informs Japan's peacebuilding policy that emphasizes the norms of state sovereignty, effective hierarchical governance, and socio-economic development as key legitimizing principles. A historically-grounded approach to the foundation of Japanese peacebuilding policy highlights the need to reconsider the taken-for-granted assumptions about the homogeneity of the liberal peace. More generally, the much-needed debate about the role, vision, and agency of non-Western peacebuilders offers a promising avenue for future research.