"One of the stories they told me during my visit concerned the fate of German Communists, many of them Jewish, who had been in exile in the Soviet Union in the late 1930s. As a sort of perverse good-will gesture, Stalin handed these German Communists over to the Gestapo after the signing of the Nazi-Soviet Pact. They were, of course, immediately sent to concentration camps."
January 1, 1970
https://en.wikiquote.org/wiki/Joseph_Stalin