Leon Trotsky
"The Twin-Star: Hitler-Stalin"
End of November or beginning of December, 1939
(NY: Merit Publishers, 1969), p. 17.

"His probable participation in the war on the side of the Third Reich,
Stalin covers with a promise to 'sovietize' Germany. . . .

"The idea of Stalin's sovietizing Germany is as absurd as Chamberlain's
hope for the restoration of a peaceful conservative monarchy there. Only
a new world coalition can crush the  German army through 
a war of unheard-of-proportions. The totalitarian regime can be
crushed only by a tremendous attack on the part of the German
workers. They will carry out their revolution, surely, not in order
to replace Hitler with a Hohenzollern or Stalin.

"The victory of the popular masses over the Nazi tyranny will
be one of the greatest explosions in world history and will
immediately change the face of Europe."

[Why the above quote was wrong: Stalin did not side with Hitler;
Stalin did Sovietize Germany, "East Germany," and German "workers,"
which were not a proletariat, did not rise up in socialist revolution.
In fact, they did not even overthrow Hitler to replace him with another
bourgeois.]