While the twentieth century saw the rise of nationalism in many parts of the world, the experience of ethno-national groups within the Soviet Union deserves particular attention. Faced with the reality of governing the vast, multi-ethnic territories of the former Russian Empire, the Bolsheviks devised and implemented a set of strategies intended to confront the rising specter of nationalism. State policies initiated in the 1920s aimed to construct and reinforce ethno-national identity among the diverse groups that inhabited northern Eurasia from the Baltic Sea to the Pacific Ocean. This work examines these policies and shows how they came to play a significant role in group identity formation in the second half of the twentieth century and the violence that erupted in the Caucasus at the collapse of the Soviet Union. In addition to a detailed longue duree qualitative exploration of the process by which Soviet policies fostered deeply ingrained national identities that became powerful organizing tools in the post-Soviet era, this work also pursues a quantitative examination of demographic data compiled by the Russian Empire, the Soviet Union and the post-Soviet states to show that ethno-national homogenization of territory in favor of the titular nationalities was a process that began long before the violence and acts of ethnic cleansing that occurred with the fall of the USSR and that these demographic changes correlate with the different periods of implementation of nationalities specific policies.