Crucially Abstract Expressionism, or ‘Ab Ex’ (as I always call it for short), happened at a juncture when nearly all the major movements of the first half of the 20th century had more or less run their course. I’m thinking particularly of Cubism, Surrealism, German Expressionism, Fauvism and Neo-Plasticism. Furthermore, New York in the 1930s and 1940s offered extraordinarily rich opportunities for the emergent artists to come into direct contact with the artworks of these earlier movements.

For example, the city’s Museum of Modern Art (MoMA) ran one exhibition after another charting the development of Modernism. These ranged from ‘Cubism and Abstract Art’ and ‘Fantastic Art, Dada, Surrealism’ (both 1936) to ‘Large-Scale Modern Paintings’ (1947) – not to mention a slew of big monographic shows devoted, for instance, to Henri Matisse (1931), Pablo Picasso (1939) and Paul Klee (1941). Additionally, MoMA held other shows featuring the three great Mexican muralists – Diego Rivera, José Clemente Orozco and David Alfaro Siqueiros – as well as what were perceived as the non-European sources for Modernism, among them Aztec, Mayan, Inca and African art. The Mexicans exerted a great influence on Jackson Pollock from the late 1930s onwards and even the ever-independent Clyfford Still based at least one 1936 painting on a sculpture in the museum’s ‘African Negro Art’ show of the previous year. Likewise, in 1941 at MoMA, Pollock witnessed at first-hand Navajo artists execute a sand painting on the ground – there’s no doubt this was a factor that, six years later, led him to place his canvases on the floor. Private galleries in Manhattan, such as those run by Pierre Matisse, Julien Levy and Curt Valentin, added their own complement by exhibiting, say, Joan Miró, Giorgio de Chirico and Piet Mondrian

In effect, therefore, the Abstract Expressionists were living in a veritable museum without walls at precisely the stage when they were discovering themselves. The net result was that an exceptional array of sources, references and touchstones fed into Ab Ex, making the final mix altogether idiosyncratic (and I haven’t even touched upon the ideological layers). Indeed, they render Ab Ex such a complex phenomenon that it eludes the neat definitions that are handy for enclosing whatever constitutes a ‘movement’. Without wishing to deny the depth and breadth of Cubism, Surrealism or, later, Pop Art, some would say that Ab Ex at least matches and arguably even exceeds their intricacy and diversity. This alone makes Ab Ex different from what had come before. It incorporated most of those earlier things – and then some.

Quite simply, too, the fully mature art looks little or nothing like what came before it. Surrealists, such as André Masson and Max Ernst, may have dripped paint and allowed the motion of their hands free play – what is called ‘automatism’ – yet there is no real equivalent in pre-Second World War art for how a classic 1947 – 50 pouring by Pollock strikes the beholder. Similarly, although we may well see the influence of Matisse, Pierre Bonnard and even Mondrian in Mark Rothko’s hovering chromatic rectangles from around 1950 onwards (pictured), these imageless icons are utterly his own.

No. Ever since the American art critic Robert Coates thought to apply the term “Abstract Expressionism” to this art in 1946, observers have been trying to square the circle by making the work’s diversity into something more neatly cohesive. In 1955 a far more influential critic, Clement Greenberg, sought to unify the artists according to the notion that their output was somehow especially “American”. The problems with this approach are, first, that it reflected a Cold War context whereby the nation’s culture had to beat other contenders – in this case, Europe. Secondly, defining art in national terms is tricky because ‘Englishness’ or ‘Americanness’ can tend to lie in the eye of the beholder and thus be stretched to accommodate whatever ideological currents are in play.

Later, Irving Sandler published The Triumph of American Painting: A History of Abstract Expressionism, in 1970. Apart from apparently playing the nationalist card in its title – as some detractors have argued – the book divides its subject into two balanced camps. On the one hand, there’s the ‘gesture’ painters and, on the other, the ‘colour field’ exponents. The problem here is that the categories don’t altogether hold water. Rothko insisted that his vision was rooted in violence and not about colour, while Pollock’s linear fields are often packed with hues both delicate and bold – witness, among many possible examples, Blue Poles (1952). Much the same applies to Willem de Kooning (Woman as Landscape, 1965–66), in whose works the gesture is undoubtedly important yet who, again, was a consummate colourist, even when (like Kline) he used black and white. 

Another issue is that we’re not just talking painting. All of the Abstract Expressionists created significant works on paper, not to mention Conrad Marca-Relli’s very powerful large-scale collages made with canvas and mixed media (Ornations, L-R-4-57, 1957, pictured). The sculptor David Smith stressed that he belonged with the painters, and the same can be said of Louise Nevelson, whose sculptures present monochrome totemic presences redolent with mythic evocations of time and space. Photography has its place as well, starting with Aaron Siskind’s equivalents to Ab Ex paintings (Chicago 8, 1948, pictured) and extending to how photographers such as Barbara Morgan and Harry Callahan took energy, motion and nature’s rhythms as their subjects.