What is Britain had not entered WWII

[Mount Suribachi]

First of all, we should remember that following Chamberlains resignation Halifax was actually first in line to be the new PM, it was only when he failed to step forward and take the job that Churchill became PM. Halifax, lest we forget, was in favour of negotiating a peace with Germany at this point.

After that, it actually comes down to the age old question - could the Soviets have defeated Germany on their own? I'm actually one of the few who say no they couldn't. Without Britain in the war, America would not be at war with Germany, and between them both countries supplied huge amounts of materiel to Russia, as well as the fact that a significant chunk of the German army had to be devoted to fighting in Africa, Italy and France.

No UK/US means no support for the resistance in occupied Europe, means less troops required to garrison them, means more troops on the Eastern Front. Furthermore, reading accounts by resistance fighters, early in the war the occupied countries were garrisoned by old men and low quality units. As the resistance intensified veteran units began to perform garrison duties

No UK/US means no threat of invasion. From memory the Germans had 58 divisions in Northern France on D-Day, many of them high quality, veteran units. What difference would just half of those units have made in the East?

No UK/US means no war in N Africa. The Germans lost more men in Tunisia than they lost at Stalingrad.

No UK/US means no bomber offensive. Aside from the disruption this caused to German production of materiel and oil, and the destruction of the Luftwaffe, one cannot underestimate the effect that this had in terms of AAA. 75% of all 88mm guns produced had their barrels pointed at the sky to protect Germany from Allied bombers. There were 40,000 AA guns on the Kahmhuber line. What would those tens of thousands of 88s have done on the Eastern Front shooting at T-34s instead of Lancasters?

[Shaka_Khan]

The West was wary of both the Nazis and the Soviets. If the Soviets and the Germans somehow fought each other without invading another country, then France and Britain would probably have been happy to stay neutral.

[ShadesPanther]

The West was wary of both the Nazis and the Soviets. If the Soviets and the Germans somehow fought each other without invading another country, then France and Britain would probably have been happy to stay neutral.

And then crush the winner while it was weakened. Such is life

[spmetla]

If Britain had not entered the war a lot of things would have not happened as well. The Germans wouldn't have need to secure their Scandinavian steel supply so no Norwiegen invasion would have been nessesary. The Invasion of France (Assuming they still go through Belgium) would have ended a short bit sooner (No British Expeditary force). The Italians would have been able to retain Lybia and Ethiopia.
Assuming then that the Germans would still have decided to invaded the USSR in 1941 that would have probably have happened a few months sooner because they either wouldn't have needed to help the Italians in Greece or perhaps Italy might not have even invaded Greece. This earlier invasion would probably have allowed the Germans to advance farther faster because they wouldn't have needed to have entire Luftflotten (Air Fleets) covering Britain and the Mediterrean. Also the Germans would have had more material at their disposal and without Allied Bombings on Germany and occupied France lost material would be more easily replaced. The Luftwaffe would also have had many more planes and would have been able to retain the experienced cadre that were lost in the Battle of Britain and the Mediteranean. Also no Desert Fox!
Taking this into mind the Germans would have probably been able to have at least stepped foot in Moscow before winter would have set in. Assuming then that Soviets kept on fighting instead of surrendering it would have become more of a war of attrition then. The Soviets wouldn't have been able to recieve any lend lease (it did happen and help) and possibly not US lend lease. Thinking about it the framework for Lend Lease was only set up to help Britain and I doubt that Roosevelt would have gone out of the way to set up a system to help Communists.
I believe that the Germans would have then been strong enough to take on the Soviet Union. With a single front war the Germans would have been able to take European Russia. Granted the Russians had plenty of manpower but if there was no foriegn aid the Soviets wouldn't have been able to outproduce the Germans.
The Japanese would probably still gone to war with the US but there would probably have been no Pearl Harbor attack because that plan was inspired by an early WWII attack on an Italian navy port by a British carrier force that sunk several heavy ships. How the US would have fared in the Great Fleet battle scheme that the Japanese had I don't know, would probably be an even match between the capital ships but then the Japanese would have had the more experienced pilots. Also with no Britain as a launch point for Invasion a Europe first policy would have been impossible and the Atlantic would probably have just been a battle of sea lanes by the US against Uboats and a defensive action against US naval probes by the Kriegsmarines surface force. The Germans would probably have finished their aircraft carrier and their surface fleet would have not been damaged by the British as badly (especially from the lack of a Norwegian campaign). The Japanese also wouldn't have need to have forces in Burma or defending against Australia so they would have more forces to continue their war against China or to pit against the island hopping campaign of the Americans (supposing that was still the strategy chosen).
The Japanese-German/Italian Sea lanes would have remained open (Ethiopia to Japan) and who knows what material and technology would have been transfered.
American Military technologies wouldn't have advanced as far (except for their continuing nuclear program) the P 51 would never have been because it was designed for the British (because the US refused to build existing British war machines because they thought a British defeat was imminent)and even if it was built anyhow it would probably have still held on to those crappy Allison engines. American tank technology would probably have slowly advanced but wouldn't have benefited from the lessons learned by the British in North Africa, maybe the Grant tank would have been the pinnacle for a while.
As a side note the Spanish might have decided to join the war but who knows.

Anyhow my summary, Germans beat or stalemate USSR, Japan vs America is even match but probably US victory after invasion of Japan (I doubt that the B29 would have been developed if the Army Air Corps hadn't had the experince of bombing Germany) or it would have been a stalemate war with an eventual truce.

So yes German Europe, Italians still have small Empire and Japan vs US is only wildcard.

[Rodion Romanovich]

I don't think Britain would have been able to stay out of the war. It was Mussolini's ambition to take the British colonies in North and East Africa, so if Britain hadn't set up an ultimatum and taken part in the war from start they would have been drawn into it. The only difference is that the British would have suffered a lot more casualties and maybe they'd even have run a risk of being invaded (especially if the Germans had been able to take over the ships of the Vichy fleet), and less chances of Free French, Free Polish and other exile forces being formed. But the key question is if Britain staying out of the war would have led to very different high-level strategical decisions from the German leadership. Would they have invaded a country they didn't historically invade? And would they have chosen different occupation policies in for example France? There would still have been room for so much different decisions in those aspects that the war could have gone either way depending on what decisions were made.

[Aetius the Last Roman]

Let's not forget that the invasion of Greece setback Operation Barbarossa for a month, critical time which the Germans could have used to take Moscow.

Arguably German victory would be most likely with this in mind.

[Justiciar]

Less anti-fascism, and a possible government under Mosley?

[ehooper66]

with no dak in Africa and no 200,000 troops stationed in Norway and getting the 500,000 that were stationed in france along with all of their air force now committed to Russia the war would be over at the latest September 1942

[Seamus Fermanagh]

with no dak in Africa and no 200,000 troops stationed in Norway and getting the 500,000 that were stationed in france along with all of their air force now committed to Russia the war would be over at the latest September 1942

Too many variables to make that claim, though I lean towards your view of a Nazi victory over the Soviets.

Pretty good necrothredia effort

[ReluctantSamurai]

To me there is a fatal flaw in the idea that Britain would just stand by and allow it's closest ally at the time, France, to be overrun by the Nazi's. Hitler certainly had his eye on the Soviet Union from the beginning, but he could not allow the French Army (which, IIRC, was larger in terms of manpower than the German Army) to stand intact in his rear while he conducted military operations to the East. Hitler made a lot of stupid military moves, but leaving the French intact on his rear while he invaded the SU wouldn't have been one of them.

Britain would lose all political credibility if it stood by while Germany invaded France.

As far as affecting Japan's intentions in the Pacific, Britain would inevitably be draw in to the war because the Japanese simply could not afford to leave the major naval base of Singapore in the hands of the British while they took over the oilfields of the DEI. And oil was the primary factor in Japan's planning for war in the Pacific.

Bottom line...there is no conceivable way that Britain would not enter the war, either to honor it's commitment to France, or to defend it's interests in the Pacific.