Short answers, pulled from the story.
Jackson Pollock perfected his action painting technique in the late 1940s. He laid unstretched raw canvas directly onto the floor of his studio to allow him to walk around the work and attack it from all four sides. This radical shift in physical engagement transformed the act of painting from a static observation into a dynamic, full-body performance.
European exiles such as Max Ernst, André Breton, Piet Mondrian, and Hans Hofmann fled the Nazi onslaught to find safe haven in the United States during the war. These artists brought radical ideas of Surrealism and Cubism to New York, creating a new language that combined the emotional intensity of German Expressionism with the anti-figurative aesthetics of European modernism. Hans Hofmann taught a generation of students who would come to dominate the scene, including Lee Krasner and Jackson Pollock.
Harold Rosenberg coined the term action painting in 1952 to describe a new aesthetic perspective. He argued that the canvas was no longer a surface to be decorated but an arena in which to act. For artists like Willem de Kooning and Franz Kline, the finished painting was merely a residue of the struggle that took place upon it.
The rise of abstract expressionism coincided with the onset of the Cold War, leading to a complex relationship between art and politics. The CIA secretly funded and organized the promotion of abstract expressionists as part of a cultural imperialism campaign to demonstrate that the United States was a haven of free thought and free markets. Tom Braden, founding chief of the CIA's International Organizations Division, later admitted that this was one of the most important divisions the agency had.
Women artists such as Lee Krasner, Joan Mitchell, Helen Frankenthaler, and Louise Nevelson played a crucial and often overlooked role in the development of abstract expressionism. Lee Krasner introduced her husband Jackson Pollock to Hans Hofmann, while Louise Nevelson created monumental assemblages that became iconic to the style. The 1951 Ninth Street Show, curated by Leo Castelli, featured many of these emerging artists.
By the early 1960s, the cultural reign of abstract expressionism had begun to diminish, giving way to new movements like Pop art and Minimalism. Artists such as Andy Warhol, Claes Oldenburg, and Roy Lichtenstein achieved prominence in the United States, while Richard Hamilton led the way in Britain. The abstract expressionist emphasis on individualism was rejected by the next generation, who sought to create art that was more accessible and less personal.