On September 17, 1939, the Soviet Union invaded Poland, which then fought alone with the troops of Nazi Germany. In Belarus, September 17, by the decision of Alyaksandr Lukashenka, will be celebrated for the first time as National Unity Day. In June, Belarusian President Alexander Lukashenko signed a decree introducing a new National Unity Day holiday. It will be celebrated on September 17, which official historiography describes in Belarus as the day of the anniversary of joining the lands of western Belarus to the Belarusian Soviet Socialist Republic.
On the eve of the "holiday" celebrated by Lukashenko, the President of the Institute of National Remembrance recalled the chronology of events leading to aggression in September 1939.
"Based on the Ribbentrop-Molotov Pact, an agreement signed in Moscow on August 23, 1939, the Soviet Union, attacking Poland on September 17, as an actual ally of the Third Reich, entered the war on that day and as a next step annexing part of Finland, the Baltic states and part of Romania,” we read in the article by Dr. Nawrocki.
As he added, "after the Soviet aggression against Poland on September 17, 1939, the basic form of political repression, apart from arrests, were deportations".
Source: Poland Daily 24, niezalezna.pl