World War 2 begins in 1938 with Hitler getting his invasion of Czechoslovakia. Halder loses his nerve and does not pull off the coup. Czechoslovakia falls, but not before Britain, France, and the USSR declare war on Germany. The Poles, trying to curry Hitler's favor and deciding they can pick up on some territory from the Soviets, jump in remain on Germany's side. And the failed invasion for now, so Germany tries Schlieffen Plan 2.0 in the Summer of 1939 only for things to bog at the Franco-Belgian border. Things get World War 1 esque in the west for 1940-42 in the strategic sense. On the tactical-operational level, various attempted offensives by both sides achieve some success before being stopped by counter-moves from the other side. But it is clear that Anglo-French strength is growing.
On the Eastern Front, the initial Soviet invasion of Poland goes poorly, but so does the Polish counter-invasion (as Germany can only lend a little support, being concentrated against the French, they are far worse equipped to invade the USSR in 1938-39 then even the Germans in 1941 and the Soviets still have a fully intact Stalin line to fall back on). But the start of the war does shot-cut the purges and kick-start the Soviet learning process. The Eastern Front likewise remains static as the Soviet steadily build up their forces and experience, although there are botched offensives from both sides in the interval (the Germans aren't strong enough to mount a major invasion while also fighting the Anglo-French and the Poles sure as hell won't pull it off by themselves). But it is likewise clear that Soviet strength is growing.
Hitler, more angry at the situation by the day, manages to dodge a renewed assassination plot by some generals realizing how screwed they are and imposes a brutal crackdown upon the German command that finally consolidates Nazi power over Germany once-and-for-all. Unfortunately, the war situation means he is still screwed.
Meanwhile, the continuing Japanese war in China prompts the US to slam down the OTL embargo only somewhat later then IOTL. In a slightly more rational moment then OTL, the Japanese decide on the principle of "one war at a time": they'll strike the US at Pearl Harbor, take the US territories in the Pacific, beat the US in decisive battle thereby forcing the US to sign a humiliating peace deal, and only then do they invade and seize the European colonial possessions. As I said, slightly more rational.
Steps 1 & 2 (strike at Pearl Harbor and take the US territories) go off without a hitch. Step 3... not so much. The Japanese score their "decisive victory" at Wake, sinking a pair of aircraft carriers only for the US refuses to sign peace anyways. Only as the US navy grows in power and the Japanese oil stocks run out in late-1942, do the Japanese realize they might have bit off more then they could chew.
In 1943, the Soviets and Anglo-French launch crushing offensives against the Germans and Poles. Territorially, these offensives gain a lot but are not decisive (only up to the Rhine in the west and up to the Vistula in the east) but they break the back of the German-Polish armies. Likewise, the US drive across the Pacific starts to get under way when the rebuilt US carrier force, with even better ships, crews, pilots, and aircraft then 1942, annihilates it's Japanese counterpart in June in the Marianas.
So as 1944 comes around, the "New Entente" (USSR, Britain, and France) are preparing to deliver the deathblow to the "New Central Powers" (Germany and Poland) while the US is liberating the Pacific at a much more rapid rate.
But there are tensions in the alliance: the Anglo-French are concerned at the size and strength of the reformed Red Army along with the Stalin making talk about "redrawing some borders in the east". And while they are glad the US is dealing with the Japanese threat, they are conscious that the US navy is now the most powerful on the planet and the US is still exercising some complaints about "old-style European imperialism in Asia". And (largely) unknown to each other, the Western Entente (Britain+France), the Americans, and the Soviets are all fervently and simultaneously working on a new bomb which promises the power to annihilate entire cities.
Although I suddenly realized this still leaves out Italy, hmm...