Final answer:
The ten-year nonaggression pact, known as the Nazi-Soviet Pact, was signed between Adolf Hitler of Germany and Joseph Stalin of the Soviet Union in August 1939.
Step-by-step explanation:
The ten-year nonaggression pact, known as the Nazi-Soviet Pact or the Molotov-Ribbentrop Pact, was signed between Adolf Hitler, the leader of Nazi Germany, and Joseph Stalin, the premier of the Soviet Union. This treaty, signed on August 23, 1939, pledged that both nations would not engage in aggression against each other and outlined a secret protocol for the division of Poland and other Eastern European countries between them. The pact was crucial for Hitler as it allowed him to invade Poland without the fear of Soviet intervention, marking the beginning of World War II in Europe.