"The resistance collapsed because Poland was attacked from behind. Poland indented to resist in the barely-accessible in autumn Eastern parts of Poland. The gradual withdrawal to the East was in the plan. "
False. The condition for Polish forces I described is found in the West Point map series for WWII in the European theater of operations, linked below. The Polish Army is in the condition I describe by 14 September, 3 days before the Red Army moved an inch.
https://www.westpoint.edu/sites/default ... rope06.pdf
And even the map that shows Polish situation by 22 September shows that German forces had surrounded every single significant concentration of the Polish Army by 22 September, even the two Polish divisions at Byalostock!
https://www.westpoint.edu/sites/default ... rope07.pdf
So your claim above is hilariously non-factual.
"The (genocidal) Stalinist Russia wasn't going to pull capitalist chestnuts out of the fire for the benefit of its enemies (i.e., Britain and France.)"
The USSR was going to wage war to thwart Adolf's ambition for a "Drang Noch Osten" to take land for the German plow from the Slavic untermensches, Poles and Ukrainians very much included.
"Even more preposterous is the idea that Russia was going to fight Germany alone (and for years) - as it was obvious France had no offensive capabilities in 1939."
Without the booty Germany seized in France in 1940, the Axis war economy is a very shaky affair, as Tooze's "The Wages of Destruction - The Making & Breaking of the Nazi War Economy"
"When the British committed themselves to the defense of Poland, they simultaneously handed over to Russia the only thing Russia needed - a prospect of a devastating war between capitalist countries without its involvement. Russia simply didn't need and shouldn't have been involved in that."
Given the fate of HMG's guarantee of Czechoslovakia, one would be foolish to place any reliance on a "guarantee" so shot through with loopholes & qualifications as HMG's guarantee to Poland. Which is why the Soviet gvt were holding out for a full-dress warfighting alliance with all the trimmings at the Moscow military staff talks.
"The talks between the Allies and Stalinist Russia didn't collapse because Poland refused"
Up until a mere 3 days before the planned commencement of the German attack on Poland, on 26 August, the Polish attitude was indeed refusal. And even at that very late date, there was no indication that the Polish gvt would actually accept Soviet troops operating on Polish soil in the event of a German attack on Poland. Three days is precious little time for the planning & coordination of joint defensive operations on the scale required to prevent the historical prompt & total collapse of effective resistance by the Polish Army.
"The Allies were reluctant to sign the more important political agreement because Stalinist Russia wanted to be paid for its services with a free hand in Eastern Europe, with the right to sovietize Eastern Europe."
What the Soviet gvt actually proposed was a force to intervene in the event of a German attack on Poland, and an inter-Allied occupation of the Baltic ports.
The actual alternative to that being the prompt & total conquest of all of Poland & likely German occupation of the Baltics subsequently.
Somehow this actually existing alternative seems not to upset you as much as what happened historically.