What is Britain had not entered WWII

[spmetla]

Simply not true, IMO, for all the reasons I've cited. I'd be curious as to what leads you to believe that either the US, the UK, or France would even remotely entertain such an idea

The very things you cite though point toward the inherent distrust between France, the UK, and the USSR.

The USSR were seen as co-belligerents during the Spanish Civil-War. The threat of exporting revolution and sponsoring socialist and communist movements in France and UK were seen as a threat.

Bear in mind that the Soviets were exclude from the discussions at Munich because they were seen as too likely to hole the chance for peace.

Up to the signing of the Molotov-Ribbentrop pact the soviets were negotiating for a full alliance with France and the UK which was refused.

I think it's unlikely that any of the Western powers would fight alongside or ally with the Germans but I was thinking more of an invasion of the USSR to secure interests and prevent German take over there. Sorta like Operation Roundup was planned in case the Nazis collapsed quickly and the US and UK would have needed to seize as much formerly occupied territory in order to prevent Soviet occupation there.

The eventual alliance was just one of convenience. The Germans were the bigger threat. Ten years earlier the Bolsheviks were seen as the bigger threat. If the Germans looked as they were to be satisfied with Poland and not make war with France whats to say that the Allies wouldn't be hostile to the Soviets which were always a threat to British and French interests in the Balkans, Turkey, Iran, and the Far East. An Alliance with Germany is a step too far, yes but hostility toward the Soviets should surely be thinkable, right?

It appears to me that even before Poland was attacked, that Germany was perceived as the primary enemy by all involved, and that alliance overtures were made by each. (Now there would be a much more plausible what-if....a USSR/British/French alliance going to war with Germany)

That alliance was far more likely but in this scenario in which the British and French abandon Poland they'd be left with another German diplomatic or military victory over Poland. Assuming molotov-ribbentrop pact is still implemented that would leave the Soviets taking the role of the belligerent bugbear in international politics as they take the Baltic states, fight the winter war, and sieze bessarabia. This would leave the Soviets as the most recent 'bad guy' in public portrayal.

Only Britain was in any kind of position to bring forces to bear against Japan. The Dutch had only minimal forces covering the DEI, and France had even less. Britain had two major naval bases, Colombo on Ceylon and Singapore in Indonesia. Both have extremely long and vulnerable supply lines, and neither was in any sort of readiness to resist the Japanese (the Malayan campaign took only six weeks concluding with the surrender of Singapore on 15 Feb 1942). With only 150 or so front-line aircraft (the Brewster Buffalo as the main fighter) ) and Force Z consisting of two antiquated BB's and four DD's at the ready, the outcome is a foregone conclusion (as events showed). Colombo is probably outside Japan's logistical reach, but her subs are much more capable of interdiction than Britain's, and could conceivably render the base useless.

In this alternate scenario the Western powers would have no pressing commitments to defend Britain, the Mediterranean and those Atlantic sea lanes. While the Asiatic fleets and forces were all at a minimum for all the above powers they had far more to draw upon together than Japan.

A Japanese war against the British, French, or Dutch would bring either of the other two powers in and eventually far more forces to bear than the Japanese could match.
Who's to say the Burma and Malaya campaigns would go as they did in our timeline if the British weren't sending all from the factory and training depot to defend their island and fight in North Africa. Same for the French and Dutch. Only the Dutch were truly and completely vulnerable but a war against them brings the bigger powers in which would never give the Japanese the breathing room to exploit the seized resources and refineries.

As for vulnerable supply lines the Japanese could only threaten the Indian ocean and perhaps the South Atlantic. The waters off South East Asia and Indonesia are shallow and bad for submarines, especially of the size and slow dive time that the Japanese used. The Japanese could threaten theater supply lines but not the means of production in their European homelands.

As for the Japanese sub fleet, it is one of examples of outstanding failures in WW2. While technically the subs were good they employed poor tactics throughout the Pacific war and were very slow to adapt to the interdiction role of the submarine. The only thing the Japanese submarine force had better than the competing navies was it's good reliable torpedoes at the start of the war.

The British submarines service adapted quickly to the needs of the Mediterranean environment and their small showing in the Far East only points to their likely adapting well to that theater as well. As for their shorter range, that was never seen as much of an issue because there were far more ports and bases availble to operate out of than the Japanese which designed their subs to threaten the West Coast and Panama (both of which only suffered nuisance attacks nothing serious).

Given that Japan needed access to both China's and Korea's coal for making coke (steel-making folks...not the other kind), why would they agree to this? To say nothing of losing face to what Japan considered as a sub-human race...

I wasn't saying that they'd give up Manchuria or Korea or not take massive concessions from the Nationalist Government. A favorable peace is just that.