The Molotov–Ribbentrop Pact was a non-aggression pact between Nazi Germany and the Soviet Union that enabled those two powers to partition Poland between them. The pact was signed in Moscow on 23 August 1939 by German Foreign Minister Joachim von Ribbentrop and Soviet Foreign Minister Vyacheslav Molotov and was officially known as the Treaty of Non-Aggression between Germany and the Union of Soviet Socialist Republics.

It's clauses provided a written guarantee of peace by each party towards the other and a commitment that declared that neither government would ally itself to or aid an enemy of the other. In addition to the publicly-announced stipulations of non-aggression, the treaty included the Secret Protocol, which defined the borders of Soviet and German spheres of influence across Poland, Lithuania, Latvia, Estonia and Finland. The secret protocol also recognised the interest of Lithuania in the Vilnius region, and Germany declared its complete disinterest in Bessarabia. The rumoured existence of the Secret Protocol was proved only when it was made public during the Nuremberg Trials.