On 23rd August 1939, Vyacheslav Molotov and Joachim von Ribbentrop – the Soviet foreign minister and the German foreign minister – signed the Treaty of Non-aggression between Germany and the Union of Soviet Socialist Republics, otherwise known as the Nazi-Soviet Pact. Outwardly it was a guarantee that neither side would fight against the other in war, but a ‘secret protocol’ also outlined how Eastern Europe would be divided between the two countries. This agreement cleared the way for the Nazi invasion of Poland just nine days later.

Stalin’s Communist USSR distrusted Hitler’s Nazi Germany, knowing that ultimately Hitler intended to ...