This historically oriented paper deals with the role played by the Soviet Union in the Spanish Civil War (1936-1939). It is a critical synthesis of literature written on the subject in Czech, Russian and Spanish. It is divided into four sections, describing respectively: (1) the political background of the Soviet intervention (with sub-chapters dealing with the role of the USSR in the Non-Intervention Committee, transport of the Spanish gold to the USSR, interference of the USSR in Spain's domestic politics, and the activity of Soviet secret services); (2) direct military assistance of the USSR to the Spanish Republic (with sub-chapters focusing on the supplies of weapons and war material to the Republican Spain, dispatching of military specialists and advisors from the USSR to Spain, organisation of international brigades); (3) the fighting of White Russian emigration on Franco's side; and (4) evacuation of the children of Spanish Republicans to the USSR. The facts mentioned are commented upon and analysed. The paper is written in Spanish.