My guess is that Japan would not have done particularly well had they fought the USSR instead of the USA. The USA still blocking japanese oil imports would mean

My guess is that Japan would not have done particularly well had they fought the USSR instead of the USA. The USA still blocking japanese oil imports would mean they would have horrible logistical problems. Presumably, the USA would still be supporting the Soviets through the lend-lease program, so although the USSR would be fighting on two fronts, it's totally plausible they would be winning on both fronts. At least, Stalin seemed to think so - after the battle of Stalingrad, he started making public condemnations of IJ, etc. Even if the Japanese did do really well and pushed the soviets back, they'd just end up in the same situation they were in the 20's, where they controlled large swathes of eastern russia which were basically totally worthless, while also being extremely volatile. If the Japanese had attacked the USSR at the same time as Germany did, and the USA had not intervened, I guess maybe the USSR would have lost? It's really hard to say: I always have the sense that the Nazis were far more fragile than they look on maps, and engulfing a huge amount of extremely rebellious territory might have just ended up like China ended up for the Japanese.