The genealogy of etnos can be traced back, firstly, to the Saint-Petersburg anthropologists Eduard Petri and Dmitrii Koropchevskii and, secondly, to the ideology of Ukrainian national movement. The chapter examines the making of Fedor Volkov and Nikolai Mogilanskii’s ideas and in particular their solidarity with Southern Russian independence movements in what is now Ukraine. The chapter argues that the political engagement of these scholars, and their methods of describing identity, had a strong effect on the way that etnos theory became operationalized within the Soviet state.