The National Defence Council was the governing body in Republican Spain at the end of the Spanish Civil War (1936–1939). The council seized power with Colonel Segismundo Casado's coup on 5 March 1939 when it was clear that the Republicans had lost the war. The leaders hoped to negotiate an end to hostilities with the rebel forces led by General Francisco Franco. However, Franco insisted on unconditional surrender, and on 26 March 1939 launched the final offensive of the Spanish Civil War. By the end of the month he controlled the whole country. Most of the council members escaped into exile on British warships.

Segismundo Casado López was a Spanish Army officer; he served during the late Restoration, the Primo de Rivera dictatorship and the Second Spanish Republic. Following outbreak of the Spanish Civil War he sided with the Republicans, gradually rising to commander of the Army of the Centre. He is best known as leader of the coup against the government of Juan Negrín; its objectives were preventing a Communist takeover and terminating fratricidal bloodshed during the war, considered already lost. The rebels seized control of the Republican zone; in their quasi-government Casado served as the minister of defense. Negotiations with the Nationalists failed; Casado went on exile, first to Britain and from 1947 to Latin America, returning to Spain in 1961.