With the end of the war and the working out of the consequences of the Versailles Peace, the Soviet Union and Germany found themselves once again in each other's arms as victims of ostracism by the victorious Entente powers. The Treaty of Rapallo and the secret military
cooperation between the Red Army and the German High Command provided substantial benefits to both sides in the modernisation of their respective armed forces until Hitler's extreme anti-Bolshevism put a stop to the relationship in the early 1930s.

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The war against Russia will be such that it cannot be conducted in a knightly fashion. This struggle is one of ideologies and racial differences and will have to be conducted with unprecedented, unmerciful and unrelenting harshness. -Adolf Hitler