Siqueiros's life was equally devoted to painting and radical politics. The artist took up arms in 1936 to fight for the republican army in the Spanish Civil War, the conflict that spurred him to paint War when he returned to Mexico in 1939. Through his involvement in the mural movement in Mexico, Los Angeles, and New York, he not only gave public expression to his political ideals but also was led to experiment with new materials and formats that profoundly influenced all of his work, including panel paintings such as War. It is one of eleven works realized in duco paint, or synthetic lacquer, exhibited in Siqueiros's first solo exhibition in New York at the Pierre Matisse Gallery in 1940.

War combines the compressed distortions and ambiguities of Cubist space with a depiction of a monumental, heroic nude body. Using anatomy and musculature as well as shadow and light, the artist has crafted an image of anguish with the female body representing a nation in ruins, inflamed by conflict, and shattered by suffering. The figure, stretched across two compact panels, is shown lying on a red carpet with rivulets and ridges evoking a river of blood. Her calves, toes, shoulders, and right hand are taut and contorted with pain that flows from her flayed left forearm and hand. Represented in deadly gray, the arm is open to the bone, where the picture surface reveals heavily built-up paint layers and raw board. The texture, created from layers of gesso as well as duco paint and enamel spray paint, reinforces the materiality of the massive body. Molten red and creamy white colors suffuse the painting with sizzling energy. The artist's highly sculptural rendering of the subject imbues this portable picture with a mural-like power. Twentieth Century Painting and Sculpture in the Philadelphia Museum of Art (2000), p. 92.