France also had an alliance with the Soviets.
Oh, sure, they did have a treaty, which, in order to be acted upon, would have needed the submitting of an appeal to the League of Nations, and the approval of several powers including Fascist Italy. It's not an operational alliance by any means.
Yes, it's true, if there's a political will, that might serve as a fig leaf. But what I'm talking about is a casus belli
the public opinion will accept. The French public opinion would think, good, they're not coming West. The political will wouldn't be there.
And the British - no alliance, no treaty, no nothing, no casus belli.
The would have become a lot less slow and plodding in response to actual war if not the other upheavals necessary to make this timeline happen. See OTL, where announcements of mutual good feelings were made within hours, and substantive assistance came within a couple weeks.
No, substantive assistance didn't came within weeks. That said, you are still ignoring the fact that large sections of the British and French public opinion feared Communism, and even larger ones feared war.
Because their status as great powers depends on it, same as OTL.
Well, not necessarily. It's entirely possible that the reasoning would exactly be: "if we stay out of the war and don't waste our treasury and young men's lives, we'll be the great powers standing at the end of it".
Nonsense. The air war would have been subject to the same gradual tit-for-tat escalation that culminated in the London Blitz and the torching of Dresden et al that occurred IOTL. To suggest anything else is wildly discordant with what happened in real life. Yes, there were pre-war fears, but experience was something different.
The fears were not "pre-war". For as long as France was in the war as such, the French never bombed Germany and positively attempted stopping British bombers from taking off. And the British stayed well clear of truly sensitive targets in Germany until the late summer of 1940.
Now, it's true that the
slow tit-for-tat escalation took place, and that
eventually (very eventually; Dresden is in 1945) no holds would be barred. But that's looking at a war lasting years. I'm looking at a stalemate by 1941 here.
Even being very optimistic and assuming a DoW on Germany, chances are the Westerners play the drôle de guerre, and in OTL that was no air attacks on Germany.
But it caused a shock to Britain and French foreign policy that made it crystal clear they had to fight Hitler at the next juncture. Which IOTL, they did, despite the internal debate, despite having anemic allies, despite not being ready for war, all because Nazism was an existential threat. The cycle of appeasement had been played out.
Exactly. In OTL, it was, we'll have to deal with the Nazis ourselves. In this ATL, it's: there's somebody bleeding white the Nazis, to no cost for us, let's wait and see.
The fact that Poland couldn't match the Germans, in OTL (the anemic ally), is another factor pushing for involvement, not the opopsite; the Germans are likely to win out there in OTL, and therefore to become more dangerous. But in this TL, with the German-Polish troops moving into Russia
in the fall of 1939, people in the West would be thinking about Napoleon.
It's possible the British and the French sell military equipment to the Soviets for a political price. That's OK. It would be this ATL's equivalent of the US Lend-Lease. There will be economic sanctions, embargoes etc. against Germany and Poland. War, not so quickly.
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The side aspect nobody has considered until now is: would the Soviets buy it, if the alliance offer was made before the German-Polish attack?
In OTL, the Soviets were extremely wary of the Westerners' proffers - because they were thinking about the scenario above. The Westerners telling them, let's you and him fight. So, even if the British and the French really come to the unlikely decision you are rooting for, even if they timely send plenipotentiaries to Moscow - are we sure Stalin, being his usual paranoid self, doesn't think "this is a ploy to make sure the Germans and Poles attack us"?
Naturally, things change once the attack is on, and any help is welcome. But at that point, I don't believe the French and British would play the cavalry's tune.