The POD for this event is that Leon Trotsky became the leader of the Soviet Union instead of Stalin after Lenin's death in 1923. Trotsky leads a program of industrialization and collectivisation of agriculture (resulting in the extermination of the kulaks and a Holodomor-esque event in the Ukraine) until 1929.
The Great Depression occurs and in 1932, Trotsky, in accordance with the eponymous ideology of Trotskyism, prepares the Soviet Union for a war with the former Russian subjects in Eastern Europe, including Poland.
Hitler and the Nazi Party still exist and is currently running for President of Germany.
The question is: if the Soviet Union invaded Eastern Europe, would the Western Allies take action or would they ignore it as they did with Hitler?