Assume for the moment France is even more reluctant to enter war in 1939. The (secret) decision is made to avoid it at all costs until the rearmament program is completed in 1942. Britian & the USSR desperatly form a last minute alliance to support Poland, and in the first week of September 1939 are at war with Germany.

The Poles would detest Soviet support, but would they refuse meaningfull assistance? Or would the Soviet army simply march west whatever the Poles did?

How does this change Germanys military situation? What are the long range stratigic implications?