Historically Japan first looked longingly at Manchuria and the Russian East (the closeness to Japan been the attraction). It was mainly the Battles of Khalkhyn Gol that changed their minds and the territorial ambitions, and their ambitions facing south.flakbait wrote: By the same token, by suddenly striking N against the Soviet Union, this would gain Japan exactly how much oil ? From a purely strategic point of view, striking the then Soviet Union in Dec 1941 helps Japan out `how` ?
If Russia was in a significantly weaker position at the end of '41 due to greater German success in op Barbarossa, maybe Japan's decision might have been different. (But they still would have needed DEI oil).
Oil was an issue but there are means of obtaining and securing oil other than occupation. The Dutch would have keep selling them oil 'till the cows came home'. It was under American pressure that the Dutch imposed the embargo. And even then they did it with great reluctance. If Germany hadn't been occupying Holland at that moment the answer may have been quite different.