It is often forgotten that the decision by Nazi Germany to invade Poland in September 1939, and thus to start the Second World War, was only made possible by a secret agreement with the government of the USSR. The Molotov-Ribbentrop Pact of the previous month contained clauses that partitioned Poland into German and Soviet zones of influence and allowed Russia to drive into Poland from the east while the Wehrmacht struck from the west.
On this date in 1939, German and Soviet forces met, and in token of their victory over Poland, held a celebratory military parade in Brest-Litovsk (ironically the site of a humiliating capitulation by Lenin’s Bolshevik government to imperial Germany in World War I). Standing on the platform in the photo above are two geniuses of tank warfare, Germany’s Heinz Guderian and the Soviet Semyon Krivoshein.
The Soviets occupied eastern Poland until 1941 when Hitler’s surprise attack, Operation Barbarossa, broke the peace treaty with the USSR and opened up a new front in the war. In the interim the Soviets had taken hundreds of thousands of Polish prisoners and massacred the officer class in the Katyn forest in 1940. The Red Army would return in 1944 and drive out the Germans. Their stay would last until the fall of eastern European communism in 1989.