The Vyacheslav Molotov-Ribbentrop Pact was a non-aggression treaty signed on August 23, 1939, between the Soviet Union and Nazi Germany. Named after the foreign ministers of both countries, Vyacheslav Molotov and Joachim von Ribbentrop, the pact ensured that the two nations would not attack each other for the duration of the agreement. This allowed both countries to pursue their territorial ambitions without fear of conflict with one another. In addition to the non-aggression clause, the pact included a secret protocol that divided Eastern Europe into spheres of influence. This led to the invasion of Poland by both countries in September 1939, marking the beginning of World War II. The agreement remained in effect until June 1941, when Germany invaded the Soviet Union, breaking the pact.