This chapter explores the contention that Germany and Vietnam were both divided states and divided nations before their respective (re)unification in 1990 and 1976. Politically, mountain passes marked Vietnam's seventeenth-century division into rival regions and twentieth-century schism into two republics. Nation-building in the German Democratic Republic (GDR) and Federal Republic of Germany (FRG) revolved around their competing claims to be the sole legitimate representative, or 'rightful political embodiment' of the German nation. Vietnam's accession to Association of Southeast Asian Nations (ASEAN) in 1995 signalled its readiness to pursue regionalism as part of its continuing nation-building project. The chapter argues that it was primarily in Vietnamese and German national interests to take part in regional integration, for historical, political and strategic reasons. Accordingly, regionalism is an integral part of their nation-building ideologies.