The Molotov-Ribbentrop Pact was a non-aggression agreement signed between Germany and the Soviet Union in Moscow on August 23, 1939, one week before the invasion of Poland and the outbreak of World War II. It was officially called the Treaty of Non-Aggression between the Third Reich and the Union of Soviet Socialist Republics.
It was informally called the Molotov-Ribbentrop Pact because it was signed by the German Foreign Minister Joachim von Ribbentrop and the Soviet Foreign Minister Vyacheslav Molotov. By this agreement, each country promised not to join any nation or group of nations that were at war or in a state of war with the other party. This pact was in effect until June 22, 1941, which was the date when the Third Reich began Operation Barbarossa, which was the invasion of the Soviet Union.
Secret protocol
Aside from the promise of non-aggression, the Molotov-Ribbentrop Pact contained a secret clause which divided Northern and Eastern Europe into German and Soviet spheres of influence. This agreement was an ominous forerunner of potential political and territorial rearrangements of Eastern Europe. With the green lights granted by the Molotov-Ribbentrop Pact, Germany and the Soviet Union invaded Poland in September 1939, and divided the country between them. Next, the Soviet Union annexed a chunk of Finnish territory, Estonia, Latvia, Lithuania and eastern and northern Romania.
The Non-Aggression Pact of 1939 (footage)