Jon Halliday & Jung Chang's book on Mao asserts that many in China shortly after the Molotov-Ribbentrop pact and partition of Poland believed that a Soviet-Japanese pact and partition of China were also imminent. They allege Mao hoped for this and saw personal opportunity in being the guy in charge of the Soviet sphere of influence within China.
Later on, one Japanese leader proposed partition of China with the Soviets, with the latter getting the CCP held areas. If they actually just allocated CCP base areas to the Soviets that would make for a weird, leopard-spot map. Maybe the Japanese proposer of this deal just meant Yanan and northwest China going to the USSR?
Could this have happened, and if so, how/why?
The main difficulty I see that unoccupied China was not a particularly rich or valuable acquisition for the Soviet Union.
Thoughts?
You win if you can come up w/ a plausible scenario of Soviet-Japanese partition happening. Double your points if the PoD is after the consolidation of Soviet Stalinism and Japanese military rule in the 1930s.