 When civil war broke out in Spain, Hitler and Mussolini lent military support to the Nationalist rebels, led by General Francisco Franco. The Soviet Union supported the existing government, the Spanish Republic. Over 30,000 foreign volunteers, known as the International Brigades, also fought against the Nationalists. Both Germany and the USSR used this proxy war as an opportunity to test in combat their most advanced weapons and tactics. The bombing of Guernica by the German Condor Legion in April 1937 heightened widespread concerns that the next major war would include extensive terror bombing attacks on civilians. The Nationalists won the civil war in April 1939; Franco, now dictator, bargained with both sides during the Second World War, but never concluded any major agreements. He did send volunteers to fight on the Eastern Front under German command but Spain remained neutral and did not allow either side to use its territory.
