The Molotov-Ribbentrop Pact, colloquially name after Soviet foreign minister Vyacheslav Molotov and German foreign minister Joachim von Ribbentrop, was an agreement officially entitled the Treaty of Non-aggression between Germany and the Union of Soviet Socialist Republics, signed in Moscow in the early hours of August 24, 1939, dated August 25, that 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 as the Nazi-Soviet Alliance. It remained in effect until Nazi Germany invaded the Soviet Union on June 22, 1941 in Operation Barbarossa.