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.

The Spanish Republic, commonly known as the Second Spanish Republic, was the form of government in Spain from 1931 to 1939. The Republic was proclaimed on 14 April 1931 after the deposition of King Alfonso XIII. It was dissolved on 1 April 1939 after surrendering in the Spanish Civil War to the Nationalists led by General Francisco Franco.