Previous historical scholarship on the Russian Revolution has tended to codify its political counterparts in independent south-east Europe as ‘ideological peripheries’. Nowhere have such attitudes been more pervasive than in the South Slavic Balkan territories that formed the first Yugoslavia in 1918. This paper seeks to challenge this assumption by exploring how reactions among the South Slavic Left towards the events of 1917 to 1922 were conditioned by separate processes of historical development. While the Bolshevik Revolution proved influential in radicalising much of the future Yugoslav Communist rank and file, the contours of a distinctive form of Marxist ideology, rooted in the historical contexts of its adherents’ respective homelands, had already been established prior to 1914. Although drawing from a wide spectrum of ideological currents, this ultimately coalesced around the region’s early socialist heritage, specifically the Serbian philosopher Svetozar Marković, emphasising emancipatory revolution, political and economic cooperation and active resistance to external rule. Widespread violence and repression by the armies of the Central Powers during the First World War, cemented the latter as a core tenant of Yugoslavian Communism. The significance of the Soviet Union’s founding in December 1922, was thus tied more to how it amplified these pre-existing trends, foreshadowing the rise of Titoism and Non-Alignment after 1945.