Political map of Russia & the former Soviet Union 25 November 1936 (Anti-Comintern Pact): Even more concerning to the Soviets than Japan's occupation of Manchuria (1931) (Japanese invasion of Manchuria), the deeply anti-Communist Adolf Hitler became German Chancellor in 1933 and set about rearming Germany. When the Spanish Civil War broke out in 1936, Stalin (Josef Stalin) supported the incumbent Republicans (Second Spanish Republic) while Hitler aided their Nationalist rivals (National faction (Spanish Civil War)). That same year, Germany joined Japan in the Anti-Comintern Pact, a thinly veiled alliance against the Soviet Union.