Hitler's diplomatic strategy in the 1930s was to make seemingly reasonable demands, threatening war if they were not met. When opponents tried to appease him, he accepted the gains that were offered, then went to the next target. That aggressive strategy worked as Germany pulled out of the League of Nations, rejected the Versailles Treaty, and began to rearm. Retaking the Saar Basin in the aftermath of a plebiscite that favoured returning to Germany, Hitler's Germany remilitarised the Rhineland, formed an alliance with Mussolini's Italy, and sent massive military aid to Franco in the Spanish Civil War. Germany seized Austria, considered to be a German state, in 1938, and took over Czechoslovakia after the Munich Agreement with Britain and France. Forming a peace pact with the Soviet Union in August 1939, Germany invaded Poland after their refusal to cede Danzig in September 1939. Britain and France declared war and World War II began – somewhat sooner than the Nazis expected or were ready for.