Abstract Expressionism emerged in the late 1940s as a radical new art movement in America that focused on formal qualities and emphasized the autonomy of art over political or social concerns; critics like Clement Greenberg championed Abstract Expressionism and formalism, arguing that art should separate itself from mass culture and popular tastes through an emphasis on formal innovation and medium-specific purity; Greenberg's theories helped establish Abstract Expressionism as the leading avant-garde movement in America and positioned it as an anti-communist symbol during the Cold War era.