The Molotov-Ribbentrop Pact was a non-aggression treaty signed on August 23, 1939, between Nazi Germany and the Soviet Union. This agreement not only pledged both countries to avoid military conflict with each other but also included secret protocols dividing Eastern Europe into spheres of influence, directly setting the stage for the invasion of Poland. The pact shocked many observers as it brought together two ideologically opposed regimes and played a crucial role in the events leading up to World War II.