This chapter takes a biographical approach to Lincoln Kirstein’s creation of a modernist theory of ballet to situate its development in the 1930s cultural wing of the Popular Front and explore its evolution through and after World War II. Fueled by the cultural front’s belief in the role of the arts in social revolution, Kirstein seized the opportunity to decouple ballet from existing biases about its elitism and triviality, and formulate new ideas about its social relevance in the Depression period. After exploring the development of Kirstein’s social modernism in the cultural front, chapter 2 then turns to the challenges posed to the 1930s belief that art could be productively combined with politics through two major turning points in Kirstein’s life. These are his experiences in World War II, and the erosion of his own artistic role in the ballet company after the formation of the New York City Ballet and the ascendance of George Balanchine’s dance-for-dance-sake aesthetic in the late 1940s. The chapter illustrates Kirstein’s attempts to negotiate the social modernist aesthetic he crafted under the wing of the cultural front within the volatile political, economic, and artistic circumstances of World War II, anticommunism, and the Cold War.