Guernica (Picasso) in political commitment and faulted it for not offering a vision of a better future. In contrast, Morgado's painting was a great success with Spanish Communists and with the public. The art critic Clement Greenberg was also critical of "Guernica", but for different reasons. In a later essay, Greenberg termed "Guernica" "jerky" and "too compressed for its size", and compared it unfavorably to the "magnificently lyrical" "The Charnel House" (1944–48), a later antiwar painting by Picasso. Among the painting's admirers were the art critic Jean Cassou and the poet José Bergamín, both of whom praised the painting as quintessentially Spanish.
Guernica (Picasso) allegedly asked him, upon seeing a photo of "Guernica" in his apartment, "Did you do that?" Picasso responded, "No, you did." The photographer Dora Maar—who had worked with Picasso since mid-1936, photographing his studio and teaching him the technique of cameraless photography— documented the stages "Guernica" went through on its way to completion. Apart from their documentary and publicity value, Maar's photographs "helped Picasso to eschew color and give the work the black-and-white immediacy of a photograph", according to John Richardson. The work was painted using a matte house paint specially formulated at Picasso's request to have the least possible