The focus of attention in the world of contemporary art began to shift from Paris to New York after World War II and the development of American Abstract Expressionism. During the late 1940s and early 1950s Clement Greenberg was the first art critic to suggest and identify a dichotomy between differing tendencies within the Abstract Expressionist canon. Taking issue with Harold Rosenberg (another important champion of Abstract Expressionism), who wrote of the virtues of action painting in his article "American Action Painters" published in the December 1952 issue of "ARTnews", Greenberg observed another tendency toward all-over color or Color Field in the works of several of the so-called 'first generation' Abstract Expressionists.