I think the trope would have a Soviet Russia and communist France, of course giving us a proto-Nazi reactionary Germany, but I think that is pastiche. Instead I would stalemate the war and reverse the roles, by the early 1930s you have increasingly Socialist Germany facing the increasingly right-wing Republics of defeated and humiliated Russia and France. Germany has imposed a harsh Versailles like peace upon Russia and with British influence had not done so effectively to France. The British have retreated from their alliances to each as they turn both inward and outward to redress the hated peace. Russia here without a full blown civil war is healthier, likely just as strong as the USSR had recovered Russia from WWI, going to a dictatorship as the domestic situation melts down, rearming flagrantly and spending wildly, France is as strong or weak too, both rivaling German power as the A-H Empire may be struggling with its internal issues, thus weakening the CPs even with Bulgaria in step, Romania playing along and the OE cooperating. We could have Italy going Fascist and aligning with the Franco-Russian "axis" so you get the Italians picking at the British, Japan having broken away stirring trouble in Asia and the USA never having looked beyond its continent. The British might be embroiled in disputes with the OE too, with France and Russia picking at the edges. Here you might not see enough gravity for the British to ally with Germany but they at least are no longer belligerent. I doubt the Germans are "complacent" but they might have suffered enough economic doldrums and the rapprochement minded Zentrum/SDP coalition in power feels quite appeasing and neglectful of its military commitments, so here the second world war begins in Asia with aggressive Japan, maybe war sparks between the UK and Japan, Italy lumps on to assert itself, the Russians try for Finland and France instead of investing in Maginot has gone for Lightening War. Italy goes at A-H and a reversed Barbarossa would put the German armies on the defense with a French strike into the Ruhr devastating. From there it would be a shorter but not certain war.