This project aims to analyze transborder national membership politics in Korea over the course of the twentieth century. By transborder national membership politics, I mean the contestations over the membership status of those who have long resided outside the territory of the state, do not possess the citizenship of the state, yet are represented as belonging to the nation, and are understood as having a substantial claim on the state. The project examines the contestations over the membership status of colonial-era ethnic Korean migrants to Japan and northeast China and their descendants. Using archival and ethnographic data as well as secondary literature, I will compare three cases of contentious transborder national membership politics in the colonial, Cold War and post-Cold War eras. The century-long span of this study and the distinctiveness of the case-involving both a sustained period of colonial rule and a period of belated and divided nation-state building interwoven with the Cold War-will highlight the crucial importance of three factors which have been neglected in existing literature on transborder membership politics: (1) the dynamically evolving macro-regional context, which has shaped transborder national membership politics in the region in distinctive ways; (2) the essentially political, performative, and constitutive nature of transborder nation-building; and (3) the documentary techniques of the modern state, the durable traces of which have constituted official individual identities and have thereby mediated the encounters between the "homeland state" and its "transborder nation."