The Molotov–Ribbentrop Pact, colloquially named after Soviet foreign minister Vyacheslav Molotov and German foreign minister Joachim von Ribbentrop, was an agreement officially titled the Treaty of Non-aggression between Germany and the Union of Soviet Socialist Republics and signed in Moscow in the early hours of August 24, 1939, but dated August 23. The agreement renounced warfare between the two countries and pledged neutrality by either party if the other were attacked by a third party. Each signatory promised not to join any grouping of powers that was "directly or indirectly aimed at the other party." The Pact is known by a number of different titles. These include the Nazi–Soviet Pact, Hitler–Stalin Pact, German–Soviet Non-aggression Pact and sometimes the Nazi–Soviet Alliance. It remained in effect until June 22, 1941 when Germany executed Operation Barbarossa and invaded the Soviet Union.

In addition to stipulations of non-aggression, the treaty included a secret protocol dividing the independent countries of Finland, Estonia, Latvia, Lithuania, Poland, and Romania into Nazi and Soviet spheres of influence, anticipating "territorial and political rearrangements" of these countries' territories. All of these states were subsequently invaded, occupied, or forced to cede territory by Nazi Germany, the Soviet Union, or both. Only Finland was able to resist and remained an independent democracy.

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