On the morning of June 22, 1941, three million invading German soldiers crossed the Soviet frontier as part of Operation Barbarossa. Simultaneously, Soviet supply trains bearing oil, timber, grain, and other vital raw materials, crossed westward heading into Germany. This was the last exchange of the Molotov-Ribbentrop Pact, the tenuous alliance between the Soviet Union and Nazi Germany that would inaugurate World War II.
As Adolf Hitler seized Austria, the Sudetenland and then the remnants of Czechoslovakia, the statesmen of Europe grew increasingly concerned. In the Soviet Union, communist tyrant Josef Stalin’s primary objective was to avoid war at all costs. In June 1937, the NKVD (the Soviet secret police) had begun arresting senior military officers within the Red Army. Over the next eighteen months, the Red Army’s leadership was decimated: more than 43,000 military officers were shot, arrested or dismissed. Stalin was uncomfortably aware that the Soviet Union was extremely ill-prepared for war as the clouds of war gathered in Central Europe.
Until August 1939, the Soviet Politburo and the NKID (the Soviet Foreign Ministry) sought peace through “collective security”—that is, mutual assistance pacts with Europe’s major powers. But British and French leaders failed to grasp the scale of events and also distrusted the Soviet regime. In the summer of 1939, British and French military representatives were sent to Moscow to negotiate a military alliance against Germany with the Soviets. Inexplicably, they were sent via a slow-boat, were not authorized to sign any documents and, in the British case, had not even been credentialed by their government. In light of this half-hearted effort at negotiation, Stalin kept a channel open to Germany.
Hitler was eager to reach an agreement with the Soviet Union. By mid-July 1939, he was only six weeks away from his planned invasion of Poland. Such an attack would likely draw France and Great Britain into war. To avoid the prospect of an extended two front war, Hitler needed a guarantee of neutrality from the Soviet Union. He made this clear through his Ambassador in Moscow, Friedrich Werner von der Schulenberg. On August 17, Stalin suspended negotiations with Great Britain and France. The same day, he ordered the NKID to hand Ambassador Schulenberg an official memorandum proposing a non-aggression pact. The Germans responded with alacrity, desperate to reach an agreement before the launch of their Polish war.
Less than a week later, Foreign Minister Joachim von Ribbentrop arrived in Moscow with instructions to conclude an agreement as quickly as possible. Shortly after midnight the following day, the negotiations reached their conclusion. Critically, the innocuous Treaty of Non-Aggression between Germany and the USSR (as it was formally titled) contained a secret addendum partitioning Eastern Europe between the two totalitarian regimes. The division of Poland provided Hitler with the reassurance he needed. On September 1, Europe’s Second World War began, as German forces invaded Poland from the west. On September 17, the Soviets rolled in from the east, defeating the remnants of the Polish armies. The two sides immediately began the extermination of those who might resist them. The NKVD deported at least 320,000 Polish citizens to Siberia, where nearly half were starved to death or executed. They also executed all of the Polish officers taken prisoner during the war—more than 22,000 men—in the Katyn massacre.
Poland was only the first victim. Shortly thereafter, the Soviet Government issued ultimatums to Estonia, Latvia and Lithuania, forcing them to conclude “defensive pacts” with the Soviet Union. These allowed Red Army soldiers onto their territory. After Finland refused a similar arrangement, Stalin ordered the Red Army to invade, but was forced to seek an agreement after the tiny Finnish Army inflicted more than 300,000 casualties on the Soviets over three months. This embarrassment helped to convinced Hitler of the Soviet Union’s military weakness.
Stalin’s expansionist drive—designed to create a ring of buffer states between the USSR and Germany—continued during the summer of 1940. Beginning in May, the Soviet Union occupied and annexed the Baltic states. A similar process followed in Rumanian Bessarabia and Northern Bukovina. The Soviet occupations of these border regions was brutal: tiny Estonia lost nearly 10% of its population to deportations and mass executions.
As Germany and the Soviet Union partitioned Europe between them, they also worked together economically and militarily. This cooperation was not new. In 1922, the German and Soviet militaries had concluded a covert pact to assist each other. Together, they built a network of secret military bases, testing grounds and laboratories inside Russia, where they developed new aircraft, armored vehicles and chemical weapons. Thousands of German and Soviet officers trained together at these facilities. Hitler’s coming to power terminated most of these arrangements, but beginning in 1939, military and economic cooperation resumed. From January 1, 1940 until June 22, 1941, the Soviet Union supplied Nazi Germany with “1.5 million tons of grain, 100,000 tons of cotton, 2 million tons of petroleum products, 1.5 million tons of timber, 140,000 tons of manganese [and] 26,000 tons of chromium.” In exchange, the Soviet Union received industrial goods, scientific equipment and in particular, military material. In particular, Germany provided the Soviet Union with a half-finished battlecruiser, aircraft prototypes, optical equipment, artillery pieces, and other instruments of war. Within six months of the Pact, the Germans agreed to supply Soviet submarines fighting against Finland, while the Soviets did the same for German commerce raiders. At the height of cooperation, the Soviets allowed the German Navy to open a secret naval base on Soviet soil near Murmansk to interdict British shipping and assist in the invasion of Norway.
The Molotov-Ribbentrop Pact would be shattered in dramatic fashion as German bombs rained down on Soviet cities and airfields in the early morning hours of June 22, 1941. Stalin’s efforts had led to the exact scenario he hoped to avoid. The Pact allowed Germany to defeat France, Denmark, Norway, the Netherlands, Belgium, Yugoslavia, Romania, and Greece. With Germany in firm control of the western half of the continent, Hitler could concentrate the vast resources of the German Army against his ultimate foe: the USSR. The final price of the Pact would be paid by more than 27 million Soviet citizens who would lose their lives between 1941 and 1945.
 Conquest, p. 450.
 Geoffrey Roberts, The Unholy Alliance: Stalin’s Pact with Hitler (London: IB Tauris, 1989), p. 176.