National Socialism was, to a considerable extent, a counter-movement to the international communism sponsored by Russian Bolshevism. Hence, both systems were deeply antagonistic, and had been engaged in a cold war since the end of the First World War, presaging the later Cold War between the Soviet Union and the West. Indeed, Germany and Russia were to fight a proxy war, each taking opposing sides in the Spanish Civil War (1936-39). Mutual threats of extermination were commonplace. Therefore, in the absence of any deterrent, it seemed inevitable that a military conflict would break out at some point.