Alternate War in the Pacific:
Shortly after the Great War was finished the former alliances parted and life started to go its normal way. The Great Powers, minus the unstable USSR and Germany, who was banned, agreed to limit their military spending in the hope to get a save new world. Treaties, like the Washington Naval Treaty, were signed as in the OTL. For at least a decade there indeed was peace more or less and economical growth worldwide.
With the crash of the stockmarkets at Wallstreet in 1929, the economy plunged into a bottomless pit internationally, while worldwide, the international feelings of the 20’s were overwritten by more short term locally focused national issues, such as protection of trade and recovery. The Crises resulted in the rise of anti democratic thinkings, such as Fascism and Communism, more than before and some states got a totalitarian government after some time. Germany became the most prominent Nationalist State, with the NSDAP in the lead of the government. Italy already was Fascist since the 20’s, but remained relatively dormant internationally. The USSR was still in internal turmoil, due to the internal competition of factions for the successor of the death of Lenin. Japan too changed from a Parliamentary Monarchy, to a form of military dictatorship, with the Army leading the politics in the state.
New alliances were formed, with the Germans and Italians starting with the Axis Rome-Berlin, to which was added later Japan and some smaller European states, south - east of Germany. The UK and France allied to counter German aggression against other European states, predominantly Poland. The USA want4ed nothing of this and remained strictly neutral, although the internationalist FDR as president wanted to aid the Western Allies as good as possible.
In 1939, War started when Polland was invaded by both USSR and Germany, following a declaration of War from the UK and France to Germany and the USSR. (Ribbentrop-Molotov Pact as in OTL). In 1940, the Germans conquered Western Europe, which resulted in the collapse of France and an armistice with the UK, as the new UK government saw no reason to continue the fighting on its own. (Churchill had been replaced by the more pragmatic Halifax.) War was essentially over after the collapse of France, with an intact UK and Dominion world and a more or less intact Germany, in military terms. The German Kriegsmarine had only lost a few ships, and almost no real losses in the land war. The British had lost so far only one battleship and one carrier, both in the start of the war, but nothing else. Italy had remained neutral so far, as Hitler had pushed Mussolini so far with aids and good talking, fearing that Italy might open a new front, dividing the frontlines more, than desired. There would be no war in Africa and none in the Balkan so far.
Japan was also moving into an attack position, as it already was fighting in China for several years, but did not gain much from it so far. It wanted more resources, to get an input in the economy and resources for the Army, but these wanted resources were in foreign territory.
At first the plan to wage war against the West was as originally planned in the OTL, but now Germany offered a new option, as the war in Europe was over and the USA were still out of the war. Germany wanted to keep things so, more or less, as it wanted to crush the USSR once and for all, despite the treaty they had with Stalin. Germany pointed the Japanese on the weak Dutch East Indies, as well as the oil rich peninsula of Kamchatka in the Far East of the USSR. This offered the Japanese an option to fight a limited war, against significant weaker odds, than originally planned, as the fear of the industrial might of the USA particularly was threatening enough.
The plan was the following: Germany would strike first at the USSR, early 1941, as the war in Europe already was over and the bulk of the Wehrmacht could therefore be deployed against only a single front, while secondary units were considered more than adequate to take control over the occupied lands in the West. Italy too would join from the start, as it had been left out of the fighting so far. Hitler and the Germans wanted no split in fronts, so Italy was not allowed to open hostilities against Greece, as originally proposed. Japan could go to war after six months or so, following the Germans in their war against the USSR, in order to split the USSR in a two front war, making things easy for both.
At than same time, the Japanese could also mount amphibian operations against the Dutch East Indies, who remained independent so far from the other Western Allies, while the Netherlands themselves were already occupied by Germany. The Task however was to keep the British out of the fight and so Malaya and Singapore were left out of the fighting, although French Indo China was taken over form the French, who were actually the Vichy French, already cooperating with the Germans. Hong Kong was also left alone, as it had no real military purpose. The Philippines remained under US control, but were partially independent.
A short summary of the Alternate War in the Pacific:
On the 7th of December 1941, Japan launched its strike on both the USSR and the Dutch East Indies. The Navy mounted only a limited campaign in the Dutch East Indies, as the opposition was limited and the Dutch forces spread thinly. The War against the USSR was a landcampaign, from Manchuko Province. Only a small landing took place on the island of Sakalin, to secure the oil rich bases over there. As the USSR already was six months or so in war with Germany and Italy, forces in the Far East were thinly spread, making things easy for the not all to well equipped IJA.
1942:
The remains of the Dutch East Indies were colonised by Japan and the Dutch driven out. The USSR was further invaded and the siege of Vladivostok started, as this was the only real base of the Russians in this part of the world. This siege proved a hard thing to do, as the Russians continued to counterattack from the base and small reinforcements continued to try to reach the besieged pocket.
The main war on the USSR was going bad for the Russians, as the Blitz of the Germans again and again caught them by surprise, as the inflexible structure of the Red Army did not allow quick thinking and frustrated any countermove. The War in Russia was this time commanded by a skilled military leader and not Hitler, as this time, he was in a good mood to listen to the skilled C&C officers. Although pockets of resistance remained in especially the cities Leningrad and Stalingrad, the Wehrmacht did not fall into the Russian trap of being lured into street to street fighting. It simply bypassed the cities and continue to roll further and further east, while secondary forces sieged the cities from the outside, starving them to death.
In may 24th 1942, Stalin was at his frontheadquarters in the city of Yakutsk, as the Germans had advanced so far inland already. Here he was betrayed by his own people and party officials, who were bribed by German spies to deliver him to the Germans, in exchange for a save exit. (Naturally this was not real, but real enough to let them believe so.) So said, so done. Stalin was in the end paraded through the streets of Berlin and finally executed after a showtrial.
In the meantime, the war in the Far East was concluded by the disintegration of the former USSR and accentuated by the surrender of Vladivostok in November 1942. The war was over and the new worldorder started with a large Japanese Empire in the West Pacific region, controlling most of Asia’s coastal regions along the Pacific and included the East Indies, formerly possessed by the Dutch. Economy boosted and Japan preciously kept the peace with the USA.
The Greatest power now was Germany, with a population of over 1 billion people and the largest economy and production in the world. The USA were second, mainly due to a smaller population, but also due to the boycott, it had installed itself on German goods and products. The UK remained third, as it still had all its Dominions and possessed the biggest Navy in the world in numbers of vessels at least. (The USN displaced more tonnage, having generally bigger ships.)
As long as Germany did not provoke both UK and USA, by building a large Navy or so, peace was guaranteed, since both UK and USA could not face the German Empire on land, and the Germans were inferior at sea. Japan remained in Asia and did not provoke the USA and UK, by laying claims on the Philippines or British possessions.