Interwar Polish foreign policy was already quite foolish, so it would be in character.
I know, right? The Poles needed to give a firm leg up to the Czechs and lose some suspicion of the USSR, and shouldn't have adopted such a supine attitude to Germany for so long.
A quite interesting scenario would be if Poland offers to back Czech defiance of Munich Agreement. Britain and France would wash their hands clean.
But is Munich ever signed?
The Czechs had
several times conceded to the "full demands" of the Nazis and their myrmidon Henlein, only to be presented with a new set. That was explicit Nazi policy.
If the Czechs had a reliable Polish alliance - an adequate buffer for the USSR, big enough to fight and, where the Entente are concerned, too big to fail - then they may well decide "Yeah, whatever happened to 'no territorial demands'? Piss off, Hitler." If the Czechs stick it to Germany
before Munich, Britain and France would be hard-pressed to keep clear. Before Munich, numerous people who by all means wanted to avoid a war between Germany and the Entente - including Goering, the German generals, Mussolini, and much of the British political and press elite - considered it a very serious possibility, in some cases almost unavoidable.
Chamberlain had always talked of the "dual policy" of appeasement and re-armament. British shows of force were intended to get Germany to negotiate. So what if they refused? No sensible government would, but the Nazis were not a sensible government.
Allowing the Germans to wave their willies at the whole purpose appeasement policy is a differant thing from clarifying that you won't become involved in the Heroic Last Stand of a country you already sold out.
Note that there was little hesitation in making war for a junta widely regarded as a German client now reeping what it had sowed and with a drastically inferior military position, when the possibility of negotiation did not exist.
Although Germany would eventually win that war, it would likely take several months for Germany to win a more exhausting victory than OTL Poland campaign.
The Czechs were estimated to last 3-4 weeks. Storming their mountains is going to leave the Germans severely exhasuted - and even the comprehensive rout of the Poles in 1939 badly depleted German stocks of bombs and bullets.
The Poles might make their own attacks, for example in Upper Silesia or southern East Prussia. This would be foolish, but the Polish officer class didn't think so. It would worsen their own eventualy defensive position, but could only buy a bit more time for the Czechs.
Still, once the Czechs are crushed, the Germans are badly battered, against an intact Polish army. They will win, but it will be a long, hard slog.
Quite likely, at some point Stalin would propose Berlin a M-R agreement, in exchange for Soviet help to crush the Czech-Poles, at better terms for the USSR than OTL. E.g. the German-Soviet demarcation line would stay on the Vistula instead of being moved to the Bug, but with Lithuania in the Soviet sphere of influence from the start instead of being traded for more Polish land, and/or Carpathian Ruthenia going to the Soviets.
So in 1938, with Litvinov still at the the helm, Stalin would come hard over to Molotov's policy where he had been deeply committed to Czech independance?
Only plausible - I say plausible, not likely - if the Entente snub of Munich has already happened.
Now, the Poles suddenly being overcome with suicidal pan-Slavism just after the signature of Munich is, theoretically speaking, no less plausible than their being overcome with reasoned pan-Slavism just before. This whole scenario is founded on a sudden, unlikely shift in Polish attitudes.
But you, of course, are only analysing those variations most beneficial to the Germans.
Hungary would likely step in and move to annex Slovakia, or would get it from Germany in exchange for an alliance.
Yugoslavia and Romania had adopted a fairly explicit attitude of "make my day, punk" towards Horthy, and Horthy was a sensible man. That was one of the things that made Germany shuffle back after Bad Godesberg, actually.
If Hungary for some reason
does adopt a policy of national suicide, Romania will not only attack, but also likely adopt a more unqualified pro-Soviet attitude.
Germany would then settle down for a while in order to rebuild its strength, with an aim to Barbarossa and eventual betrayal of its new "ally". Britain and France would remain spectaros.
And, as usual, more powerful forces aligning against Germany sooner must result in Germany doing better. Obviously.
Stalin would then go for annexation of the Baltics and the Winter War, and reap as meager a performance as OTL, although with Britain and France remaining neutrals, quite possibly he would press for total conquest of Finland in the end.
He waited until
exactly the moment at which inter-capitalist conflict reached a high-point (June 1940) to annex the Baltics. Now, it would only bring capitalists together. Why do it?
Answer: to construct the desperately needed military buffer. This is my biggest problem with your scenario: Stalin suddenly adopting such a stupid policy, destroying the buffer between him and Hitler without formenting conflict between Hitler and the Entente - quite the reverse.
Italy would almost surely exploit the confusion to annex Albania, and attack Yugoslavia with the help of Hungary and Bulgaria, it would win in the end (greatly helped by the defection of Slovenes and Croats).
And Slovenes? Whuh?
The Slovene attitude was generally something like '(Tito is better than) Hapsburgs are better than Serbs are better than Italians are better than Nazis (are better than Tito)', delete as innapropriate.
This would yield a rather interesting diplomatic landscape by late 1939, with all the great powers still at peace, Germany, Russia, and Italy busy rebuilding their strength, and Britain and France wary of all of them. Let's also say that the Soviet-Japanese border war occurs while Russia is still busy with Finland, so it ends in a stalemate, with Japan still persuaded it perhaps can take on Russia.
Khalkyn-Gol took place
before the Finnish debacle and involved entirely those Soviet forces that were on location.
The Soviet army in the Far East was better than the Japanese army in the Far East. That is a part of the geostrategic landscape, and the activities of the Soviet army in Europe have no bearing on it. An all-out shooting war with tanks rolling across Manchuria, that would affect Europe, which is precisely why Stalin didn't wage it.
