On this day in 1939, Germany and the Soviet Union agree to divide control of occupied Poland roughly along the Bug River--the Germans taking everything west, the Soviets taking everything east.
As a follow-up to the Ribbentrop-Molotov Pact, (also known as the Hitler-Stalin Pact), that created a non-aggression treaty between the two behemoth military powers of Germany and the U.S.S.R., Joachim von Ribbentrop, the German foreign minister, met with his Soviet counterpart, V.M. Molotov, to sign the German-Soviet Boundary and Friendship Treaty. The fine print of the original non-aggression pact had promised the Soviets a slice of eastern Poland; now it was merely a matter of agreeing where to draw the lines.
Joseph Stalin, Soviet premier and dictator, personally drew the line that partitioned Poland. Originally drawn at the River Vistula, just west of Warsaw, he agreed to pull it back east of the capital and Lublin, giving Germany control of most of Poland's most heavily populated and industrialized regions. In return, Stalin wanted Lvov, and its rich oil wells, as well as Lithuania, which sits atop East Prussia. Germany now had 22 million Poles, "slaves of the Greater German Empire," at its disposal; Russia had a western buffer zone.
On this same day, the Soviet Union also signed a Treaty of Mutual Assistance with the Baltic nation of Estonia, giving Stalin the right to occupy Estonian naval and air bases. A similar treaty would later be signed with Latvia. Soviet tanks eventually rolled across these borders, in the name of "mutual assistance," placing the Baltic States into the hands of the U.S.S.R. for decades to come. These "treaties" were once again merely the realization of more fine print from the Ribbentrop-Molotov Pact, giving Stalin more border states as buffer zones, and protecting Russian territory where the Bolshevik ideology had not been enthusiastically embraced from intrusion by its western neighbor, namely its non-aggression partner Germany. The highly vulnerable Baltic nations had little to say about any of these arrangements; they were merely annexed.