The Molotov-Ribbentrop Pact (otherwise known as the Nazi-Soviet Pact) was signed by Vyacheslav Molotov (Soviet foreign minister working for Stalin) and Joachim von Ribbentrop (Nazi-German foreign minister working for Hitler) on 23 August 1939. The pact promised that neither the Soviet Union nor Nazi Germany would attack the other. A secret part of the pact established spheres of interest, which later became a border when they also invaded and divided Poland between them.