So what happens if the French and perhaps the BEF roll into Germany from the West while the Wehrmacht is all tied up in Poland?
Sub Questions:
I know there's some debate regarding what levels of opposition they'd face in Germany's Western frontier. How far could the WAllies realistically have gotten? Just the Ruhr and stop there awaiting peace feelers? (Hohoho, Nice factories you have here Herr Hitler. Surrender? Now we're talking!) Rush all the way to Berlin to say hi to Adolf before kicking him out of power, laughing at him, and putting him on trial (assuming he doesn't die of self-induced lead poisoning)?
Now, let's give the WAllies a few weeks to mobilize, and say that by the time they cross into Germany, The USSR is also taking her not insignificant share of Poland. What do the WAllies do about it? Do they look the other way and pretend it never happened?* Do they take the diplomatic route and simply talk to Russia like a kid with his hand caught in the cookie jar, so they just go back to their old borders like this never happened? Or do they pull an Adolf '41 and go to war with the USSR?
* How I imagine that conversation going:
WAllies: Well Poland, we got rid of those Nazis. Here's all your land back.
Poland: The Russians have taken a huge chunk of our eastern frontier!
WAllies: I don't see any Russians.
Poland: They're right here, here, and here! *gestures at map*
WAllies: Oh... Um... Er... Those borders were like that before we got here.
Poland: But -
WAllies: THOSE BORDERS WERE LIKE THAT BEFORE WE GOT HERE! Also, a THANK YOU would be nice!