Not a bad idea, but it would have to be before 1933 when Japan left the League of Nations.
I do not know how strong the Chinese Communists were in Manchuria at the time, yet they would likely help the Soviets. Actually, they would probably come from all over China to help the Soviets (even though it was no longer controlled by China, but was rather the Japanese puppet Manchukuo). It would be interesting to see how the Kuomintang reacts. They were vehement opponents of the Japanese, yet they were also (obviously) enemies of the Communists. It is at the point in Chinese history where Chiang Kai-Shek would not sit idly by and allow a territory he still believed to be his be fought over by other powers.
Quite a few people in the GMD thought Soviet intervention was necessary for victory, actually.
Remember, the USSR provided the Chinese w/ thousands of planes and so forth until 1941.