Johns' breakthrough move, which was to inform much later work by others, was to appropriate popular iconography for painting, thus allowing a set of familiar associations to answer the need for subject. Though the abstract expressionists disdained subject matter, it could be argued that in the end, they had simply changed subjects. Johns neutralized the subject, so that something like a pure painted surface could declare itself. For twenty years after Johns painted "Flag", the surface could suffice – for example, in Andy Warhol's silkscreens, or in Robert Irwin's illuminated ambient works.