[Graham Boak]

They'd already been hammered by the Russians - another try would have brought the same result. Maybe not as easy, because the Japanese had improved their air power compared to the Russians, but the army was still outclassed. Good tank country, Manchuria.

The British did not have any oil-rich colonies in SE Asia. The oil was with the Dutch. The British had rubber. And tea.

The Americans had an emotional attachment to China because of years of attempted missionary activity. They would have come around to military action against Japan had the oil stranglehold failed - not that I think it would have done. Japan had to strike south or abandon years of expansion. Not an option, in their way of thinking.