From February 6 to 27, 1937, the Battle of Jarama was fought along the Jarama River near Madrid, as Nationalist forces attempted to cut the Madrid-Valencia road and isolate the capital. The battle was one of the bloodiest of the war, with both sides suffering heavy casualties, including the near-destruction of the British Battalion of the International Brigades, which lost 225 of its 600 men. The Republicans, under General José Miaja and advised by Soviet officers, held their ground, and the Nationalist offensive failed to achieve its objectives.

The Battle of Jarama inspired the famous song 'Jarama Valley,' which became an anthem of the International Brigades and was later popularized by folk singers like Woody Guthrie. The battle also featured prominently in the poetry of British volunteers, including John Cornford and Stephen Spender, who wrote about the heroism and sacrifice of their comrades. The battle's poetry emphasized the international character of the struggle, with volunteers from dozens of nations fighting side by side.