What significant event did the Nazi-Soviet Pact of 1939 contribute to?

The Nazi-Soviet Pact of 1939, also known as the Molotov-Ribbentrop Pact, was a non-aggression treaty between Nazi Germany and the Soviet Union. One of the most significant implications of this pact was its contribution to the outbreak of World War II. By securing a mutual agreement, both powers effectively eliminated the threat of a two-front war, allowing Germany to invade Poland without fear of Soviet intervention. This invasion on September 1, 1939, was the event that prompted Britain and France to declare war on Germany, marking the official beginning of World War II.

The Treaty also included secret protocols that divided Eastern Europe into spheres of influence, which further destabilized the region. This collaboration and the subsequent actions taken by both nations illustrate how the alliance significantly set the stage for the global conflict that followed, demonstrating its pivotal role in the initiation of World War II.