From July 6 to 25, 1937, the Battle of Brunete was fought west of Madrid, as the Republican Army launched a major offensive to relieve pressure on the capital and halt the Nationalist advance in the north. The battle was one of the largest of the war, involving some 100,000 Republican troops and resulting in nearly 40,000 casualties on both sides. Although the Republicans initially made gains, the Nationalists ultimately repulsed the offensive in a costly victory that demonstrated the growing professionalism of both armies.

The Battle of Brunete inspired numerous poems by both sides, with Republican poets celebrating the bravery of their troops and Nationalist poets praising their commanders. The battle also featured in the memoirs and poetry of International Brigade volunteers, including the American poet Edwin Rolfe, who wrote about the experience of combat. The battle's futility—a costly offensive that achieved little—became a theme in later war poetry, which increasingly emphasized the tragedy of the conflict.