The Molotov-Ribbentrop Pact, otherwise known as the Nazi-Soviet Pact, was signed by Vyacheslav Molotov (Stalin's Soviet foreign minister) and Joachim von Ribbentrop (Hitler's German foreign minister) on 23 August 1939. The agreement promised that neither the Soviet Union nor Nazi Germany would attack each other.
Only nine days later, on 1 September 1939, the German invasion of Poland began. On 17 September, the Soviet invasion of Poland began.
About 250,000 to 454,700 Polish soldiers and policemen were captured and interned by the Soviet authorities. About 125,000 were imprisoned in camps run by the NKVD, and 43,000 soldiers born in western Poland, which was under German control, were transferred to the Germans. In turn, the Soviets received 13,575 Polish prisoners from the Germans, which showed how close the co-operation was between the Germans and the Soviets.
On 3 September, France and the United Kingdom declared war soon because both had promised to defend Poland if it was attacked. Since neither of them was ready for war, they did nothing to help Poland for some time, but the Second World War clearly had started on that day.
- Fisher, David & Read, Anthony 1999. The Deadly Embrace: Hitler, Stalin, and the Nazi–Soviet Pact 1939–1941. New York: W.W. Norton & Co.
- Garlinski, Jozef 1987. Poland in the Second World War. Hippocrene Books. ISBN 0-333-39258-2
- Taylor AJP 1961. The Origins of the Second World War. London: Simon & Schuster. ISBN 978-0-684-82947-0