Although Soviet Socialist Realism has been narrowly defined as coercive, this dissertation demonstrates the surprising openness of Soviet aesthetics in the first half of the 20th century. My study focuses on what I call the "migrant aesthetics" of Hungarian communists who emigrated to the Soviet Union after the fall of the short-lived Hungarian Soviet Republic in 1919. Living in Moscow between the two world wars, the Hungarians became key actors in the Soviet quest for a new proletarian art, pairing committed political content with both realism and radical avant-garde tools, which they brought to the Soviet art world from Europe. The production of such hybrid aesthetics suggests that the dividing line between avant-garde and Socialist Realism was not as clear-cut as scholars have implied. The Hungarians also took the lead in the 1930s in organizing an international network of Leftist artists through the Comintern, the Moscow-based communist organization. By studying the politically committed yet aesthetically diverse aesthetics that originated in Moscow, I position the Soviet Union as an international center of modern art history, while also de-centering Soviet art histories with my focus on the Hungarian migrants. As the protagonists of my study believed in the synthesis of arts and politics, the sources of this dissertation are located not only in museums and art historical archives but also among state, party and police files. I bring my analysis of these surveillance and self-surveillance materials on my protagonists to the study of the films, paintings, fresco designs, prints and illustrations they produced between 1919 and 1956, demonstrating that for this generation of Hungarians, communism never lost its appeal—not even after the Stalinist purges, which the protagonists of this study survived. At the end of World War II, many of them returned to Hungary with the liberating Soviet Red Army, ever committed to building a communist world in their native land.