The Nazi-Soviet Pact, also known as the Molotov-Ribbentrop Pact, was a treaty signed between Nazi Germany and the Soviet Union on August 23, 1939, in which both countries agreed to non-aggression and outlined their spheres of influence in Eastern Europe. This pact was significant as it allowed Germany to invade Poland without fear of Soviet intervention, leading to the start of World War II. It also laid the groundwork for subsequent military operations on the Eastern Front and reflected the shifting alliances in Europe during this turbulent period.