"When the Red Army crossed into eastern Poland, it was greeted with wild enthusiasm and mass demonstrations by the populace, largely made up of Ukrainians and Belorussians and Jews. A contemporary account saw it this way:
'Not a shot was fired, not a bomb was dropped, and villages and townspeople, free from the terror of German air attacks, hailed the Red Army as deliverers. Russian troops themselves contributed to this feeling of relief by saying they came as comrades. Many inhabitants in this part of Poland are Jews whose number has been swelled by thousands of Jewish refugees fleeing before the Germans. Their joy was great at finding themselves safe from Nazi hands.'
The Red Army stopped at the Bug River, which coincided with the Curzon line, and most Jews were sent to safety beyond the Urals. Among them was a young man by the name of Menachim Begun, later to become premier of Israel, and an inveterate enemy of all things socialist. Still, in his UN speech, December 10, 1945, Albert Einstein expressly noted that only the Soviet Union opened its borders to Jews in 1939 and saved tens of thousands from the Holocaust, almost at a time when a ship seeking safety in Cuba, under Batista, was turned back to Germany. In 1938 the Poland of the Colonels refused to repatriate thousands of Polish Jews from Germany, thus dooming most to death. Choose your morality: immoral to cross the Polish border or moral to save the lives of thousands of Jews?
Not only that but almost immediately, Moscow returned Vilnius, occupied by Pilsudski's Poland since 1920 (by agreement with the Big Powers and the Lithuanian Smetona government) to Lithuania. There is little gratitude in politics. Whether one reads this action by the Soviet government (under Stalin) as generous, as Georgi Dimitrov did, or as a Machiavellian move by the arch-villain Stalin, still the fact remains that Vilnius was returned by Soviet Russia to bourgeois Lithuania. The only condition the Soviets made—one which one imagines needed no special emphasis—was that the Lithuanians refrain from secret negotiations with Hitler—which is precisely what Smetona and his group continued to do, as they had been doing all along."
(Bonosky, Philip. Devils in Amber: The Baltics. New York: International Publishers. 1992. pp. 86-87.)