After the Munich Agreement, the Soviet Union pursued a rapprochement with Nazi Germany. On 23 August 1939, the Soviet Union signed a non-aggression pact with Germany which included a secret protocol that divided Eastern Europe into German and Soviet spheres of influence, anticipating potential "territorial and political rearrangements" of these countries.chathamhouse.org, 2011 Germany invaded Poland on 1 September 1939, starting World War II. The Soviets invaded eastern Poland on 17 September. Following the Winter War with Finland, the Soviets were ceded territories by Finland. This was followed by annexations of the Baltic states and parts of Romania.
On 22 June 1941, Adolf Hitler launched Operation Barbarossa, an invasion of the Soviet Union with the largest invasion force in history, resulting in large battles and horrific atrocities. This offensive comprised three army groups. The city of Leningrad was besieged while other major cities fell to the Germans. Despite initial successes, the German offensive ground to a halt in the Battle of Moscow, and the Soviets launched a counteroffensive, pushing the Germans back. The failure of Operation Barbarossa reversed the fortunes of Germany, and Stalin was confident that the Allied war machine would eventually defeat Germany. The Soviet Union repulsed Axis attacks, such as in the Battle of Stalingrad and the Battle of Kursk, which marked a turning point in the war. The Western Allies provided support to the Soviets in the form of Lend-Lease as well as air and naval support. Stalin met with Winston Churchill and Franklin D. Roosevelt at the Tehran Conference and discussed a two-front war against Germany and the future of Europe after the war. The Soviets launched successful offensives to regain territorial losses and began a push to Berlin. The Germans unconditionally surrendered in May 1945 after Berlin fell.
The bulk of Soviet fighting took place on the Eastern Front—including the Continuation War with Finland—but it also invaded Iran in August 1941 with the British. The Soviets later entered the war against Japan in August 1945, which began with an invasion of Manchuria. They had border conflicts with Japan up to 1939 before signing a non-aggression pact in 1941. Stalin had agreed with the Western Allies to enter the war against Japan at the Tehran Conference in 1943 and at the Yalta Conference in February 1945 once Germany was defeated. The entry of the Soviet Union in the war against Japan along with the atomic bombings by the United States led to Japan's surrender, marking the end of World War II. During the war, the Soviet Union, along with the United States, the United Kingdom and China, were considered the Big Four of Allied powers.
The Soviet Union suffered the greatest number of casualties in the war, losing more than 20 million citizens, about a third of all World War II casualties. The full demographic loss to the Soviet people was even greater.Geoffrey A. Hosking (2006). Rulers and victims: the Russians in the Soviet Union. Harvard University Press. p. 242. The German Generalplan Ost aimed to create more Lebensraum () for Germany through extermination. An estimated 3.5 million Soviet prisoners of war died in German captivity as a result of deliberate mistreatment and atrocities, and millions of civilians, including Soviet Jews, were killed in the Holocaust. However, at the cost of a large sacrifice, the Soviet Union emerged as a global superpower. The Soviets installed dependent communist governments in Eastern Europe, and tensions with the United States and the Western allies grew to what became known as the Cold War.
Molotov–Ribbentrop Pact
During the 1930s, Soviet foreign minister Maxim Litvinov emerged as a leading voice for the official Soviet policy of collective security with the Western powers against Nazi Germany. In 1935, Litvinov negotiated treaties of mutual assistance with France and with Czechoslovakia with the aim of containing Hitler's expansion. After the Munich Agreement, which gave parts of Czechoslovakia to Nazi Germany, the Western democracies' policy of appeasement led the Soviet Union to reorient its foreign policy towards a rapprochement with Germany. On 3 May 1939, Stalin replaced Litvinov, who was closely identified with the anti-German position, with Vyacheslav Molotov.
In August 1939, Stalin accepted Hitler's proposal of a non-aggression pact with Germany, negotiated by foreign ministers Vyacheslav Molotov for the Soviets and Joachim von Ribbentrop for the Germans. Although officially a non-aggression treaty only, an appended secret protocol, also reached on 23 August, divided the whole of eastern Europe into German and Soviet spheres of influence.Encyclopædia Britannica, German-Soviet Nonaggression Pact, 2008Text of the Nazi-Soviet Non-Aggression Pact, executed 23 August 1939 The USSR was promised the eastern part of Poland, then primarily populated by Ukrainians and Belarusians, in case of its dissolution, and Germany recognised Latvia, Estonia and Finland as parts of the Soviet sphere of influence, with Lithuania added in a second secret protocol in September 1939.Christie, Kenneth, Historical Injustice and Democratic Transition in Eastern Asia and Northern Europe: Ghosts at the Table of Democracy, RoutledgeCurzon, 2002, Another clause of the treaty was that Bessarabia, then part of Romania, was to be joined to the Moldovan SSR, and become the Moldovan SSR under control of Moscow.
The pact was reached two days after the breakdown of Soviet military talks with British and French representatives in August 1939 over a potential Franco-Anglo-Soviet alliance.Lionel Kochan. The Struggle For Germany. 1914–1945. New York, 1963 Political discussions had been suspended on 2 August, when Molotov stated that they could not be resumed until progress was made in military talks late in August, after the talks had stalled over guarantees for the Baltic states,Michael Jabara Carley (1993). End of the 'Low, Dishonest Decade': Failure of the Anglo-Franco-Soviet Alliance in 1939. Europe-Asia Studies 45 (2), 303–341. while the military talks upon which Molotov insisted started on 11 August. At the same time, Germany, with whom the Soviets had started secret negotiations on 29 JulyFest, Joachim C., Hitler, Houghton Mifflin Harcourt, 2002, , page 588Ulam, Adam ,Stalin: The Man and His Era, Beacon Press, 1989, , page 509-10Shirer, William L., The Rise and Fall of the Third Reich: A History of Nazi Germany, Simon and Schuster, 1990 , page 503 argued that it could offer the Soviets better terms than Britain and France, with Ribbentrop insisting "there was no problem between the Baltic and the Black Sea that could not be solved between the two of us."Fest, Joachim C., Hitler, Harcourt Brace Publishing, 2002 , page 589-90Vehviläinen, Olli, Finland in the Second World War: Between Germany and Russia, Macmillan, 2002, , page 30 German officials stated that, unlike Britain, Germany could permit the Soviets to continue their developments unmolested, and that "there is one common element in the ideology of Germany, Italy and the Soviet Union: opposition to the capitalist democracies of the West".Bertriko, Jean-Jacques Subrenat, A. and David Cousins, Estonia: Identity and Independence, Rodopi, 2004, page 131 By that time, Molotov had obtained information regarding Anglo-German negotiations and a pessimistic report from the Soviet ambassador in France.
After disagreement regarding Stalin's demand to move Red Army troops through Poland and Romania (which Poland and Romania opposed), on 21 August, the Soviets proposed adjournment of military talks using the pretext that the absence of senior Soviet personnel at the talks interfered with the autumn manoeuvres of the Soviet forces, though the primary reason was the progress being made in the Soviet-German negotiations. That same day, Stalin received assurance that Germany would approve secret protocols to the proposed non-aggression pact that would grant the Soviets land in Poland, the Baltic states, Finland and Romania. Stalin telegrammed Hitler that night that the Soviets were willing to sign the pact and that he would receive Ribbentrop on 23 August.Shirer, William L., The Rise and Fall of the Third Reich: A History of Nazi Germany, Simon and Schuster, 1990 , pages 528 Regarding the larger issue of collective security, some historians believe that one reason that Stalin decided to abandon the doctrine was the shaping of his views of France and Britain by their entry into the Munich Agreement and the subsequent failure to prevent the German occupation of Czechoslovakia.Max Beloff The Foreign Policy of Soviet Russia. vol. II, I936-41. Oxford University Press, 1949. p. 166, 211.For example, in his article From Munich to Moscow, Edward Hallett Carr explains the reasons behind signing a non-aggression pact between USSR and Germany as follows: Since 1934 the U.S.S.R. had firmly believed that Hitler would start a war somewhere in Europe; the bugbear of Soviet policy was that it might be a war between Hitler and the U.S.S.R. with the western powers neutral or tacitly favourable to Hitler. In order to conjure this bugbear, one of three alternatives had to be envisaged: (i) a war against Germany in which the western powers would be allied with the U.S.S.R. (this was the first choice and the principal aim of Soviet policy from 1934–38); (2) a war between Germany and the western powers in which the U.S.S.R. would be neutral (this was clearly hinted at in the Pravda article of 21 September 1938, and Molotov's speech of 6 November 1938, and became an alternative policy to (i) after March 1939, though the choice was not finally made till August 1939); and (3) a war between Germany and the western powers with Germany allied to the U.S.S.R. (this never became a specific aim of Soviet policy, though the discovery that a price could be obtained from Hitler for Soviet neutrality made the U.S.S.R. a de facto, though non-belligerent, partner of Germany from August 1939 till, at any rate, the summer of 1940)., see E. H. Carr., From Munich to Moscow. I., Soviet Studies, Vol. 1, No. 1, (June, 1949), pp. 3–17. Taylor & Francis, Ltd.This view is disputed by Werner Maser and Dmitri Volkogonov Stalin may also have viewed the pact as a way of gaining time in an eventual war with Hitler in order to reinforce the Soviet military and shifting Soviet borders westwards, which would be militarily beneficial in such a war.Yuly Kvitsinsky. Russia-Germany: memoirs of the future, Moscow, 2008 p.95
Stalin and Ribbentrop spent most of the night of the pact's signing trading friendly stories about world affairs and cracking jokes (a rarity for Ribbentrop) about Britain's weakness. The pair even joked about how the Anti-Comintern Pact principally scared "British shopkeepers."Shirer, William L., The Rise and Fall of the Third Reich: A History of Nazi Germany, Simon and Schuster, 1990 , pages 541 They further traded toasts, with Stalin proposing a toast to Hitler's health and Ribbentrop proposing a toast to Stalin.
The division of Eastern Europe and other invasions
On 1 September 1939, the German invasion of its agreed upon portion of Poland started World War II. On 17 September, the Red Army invaded eastern Poland and occupied the Polish territory assigned to it by the Molotov–Ribbentrop Pact, followed by co-ordination with German forces in Poland. Eleven days later, the secret protocol of the Molotov–Ribbentrop Pact was modified, allotting Germany a larger part of Poland, while ceding most of Lithuania to the Soviet Union. The Soviet portions lay east of the so-called Curzon Line, an ethnographic frontier between Russia and Poland drawn up by a commission of the Paris Peace Conference in 1919.