This dissertation argues that the Japanese modern nation was formed not only from the inside but also from the outside, through nationalizing Japanese emigrants around the Pacific Rim. The study examines critical roles of Japanese overseas emigrants in shaping the ideologies and social movements in the Japanese empire. It discusses how the efforts made by Japanese thinkers and social educators in nationalizing these dispersed and marginal subjects were crucial to the creation of Japanese modernity. This study defines Japanese imperialism as "diasporic" in three dimensions. First, it illustrates the close and dynamic connections Japanese migration to the empire's Asian colonies and to other parts of the world. In particular, it highlights the important yet unexpected ways in which Japanese American migration influenced and transformed Japan's colonial expansion in Asia. Second, the study examines how the Japanese diasporic communities on both sides of the Pacific shaped the Japanese nation and empire at home. Third, from a more theoretical level, it explores the dual identity of Japanese imperialism between colonizer and the colonized. By examining flows and linkages between Japanese colonial migration in Asia and Japanese labor migration to America, this study charts the evolving trajectory of Japan as a colored empire in the cultural and political space between Asia and the West. This dissertation is a study of the Japanese empire from the angle of Japan's global migration. It challenges the separation between the nation-based narrative of modern Japan and the history of Japanese overseas migration. It also moves beyond the territory-based study of the Japanese empire by bridging the disciplinary divide between Japanese colonial history and Japanese American history and brings a transnational and global perspective to our understanding of the Japanese empire.