The German-Soviet Pact, also known as the Ribbentrop-Molotov Pact after the two foreign ministers who negotiated the agreement, had two parts. An economic agreement, signed on August 19, 1939, provided that Germany would exchange manufactured goods for Soviet raw materials. Nazi Germany and the Soviet Union also signed a ten-year nonaggression pact on August 23, 1939, in which each signatory promised not to attack the other.
The German-Soviet Pact enabled Germany to attack Poland on September 1, 1939, without fear of Soviet intervention. On September 3, 1939, Britain and France, having guaranteed to protect Poland's borders five months earlier, declared war on Germany. These events marked the beginning of World War II.
The nonaggression pact of August 23 contained a secret protocol that provided for the partition of Poland and the rest of eastern Europe into Soviet and German spheres of interest. In accordance with this plan, the Soviet army occupied and annexed eastern Poland in the autumn of 1939. On November 30, 1939, the Soviet Union attacked Finland, precipitating a four-month winter war after which the Soviet Union annexed Finnish territory borderlands, particularly near Leningrad. With German indulgence, the Soviet Union also moved to secure its sphere of interest in eastern Europe in the summer of 1940. The Soviets occupied and incorporated the Baltic states and seized the Romanian provinces of northern Bukovina and Bessarabia.
After the Germans defeated France in June 1940, German diplomats worked to secure Germany's ties in southeastern Europe. Hungary, Romania, and Slovakia all joined the Axis alliance in November 1940. During the spring of 1941, Hitler initiated his eastern European allies into plans to invade the Soviet Union.
Hitler had always regarded the German-Soviet nonaggression pact as a tactical and temporary maneuver. On December 18, 1940, he signed Directive 21 (code-named Operation Barbarossa), the first operational order for the invasion of the Soviet Union. From the beginning of operational planning, German military and police authorities intended to wage a war of annihilation against the Communist state as well as the Jews of the Soviet Union, whom they characterized as forming the "racial basis" for the Soviet state.
German forces invaded the Soviet Union on June 22, 1941, less than two years after the German-Soviet Pact was signed.