On 23 August in 1939, the Soviet foreign minister Yacheslav Molotov and German foreign minister Joachim von Ribbentrop signed the Molotov-Ribbentrop Pact (Nazi-Soviet Pact). It marked the beginning of one of the darkest periods in the recent history of our continent.
This pact comprised a secret protocol which discussed the partition of central Europe by the two totalitarian states. 9 Days later Germany invaded Poland starting World War II, with the Soviet Union invading on September 17. Even after World War II, many Central and Eastern Europeans continued to suffer under other totalitarian regimes.
This pact facilitated military aggression, annexation of whole states or regions and created the framework conditions for the Holocaust, deportation of nations and social groups, mass murder and ethnic cleansing. To commemorate this history, in 2008 the European Parliament designated August 23 as The European Day of Remembrance for Victims of Totalitarian Regimes.
Source: Embassy of the Republic of Poland in the United States of America and European Commission.