The Nazi and Soviet Non-Aggression Pact was a treaty signed on August 23, 1939, between Nazi Germany and the Soviet Union in which both parties pledged not to attack each other and to remain neutral if the other became involved in conflict. This agreement allowed Hitler to invade Poland without fear of Soviet intervention, thus igniting World War II. The pact included secret protocols that divided Eastern Europe into spheres of influence, fundamentally altering the political landscape of Europe during the interwar period.