So, my (limited) understanding of that period of Chinese history suggests that at least at first, Mao was allied with the KMT, and was supportive of them. However, Chiang led the right-KMT and basically began aggression against the Communists, which led to the divide between Mao and the left-MKT and Chiang and the right-KMT.
So, what if Chiang were more willing to work with the left-KMT and the Communists, and did not initiate hostilities? If the left-KMT government were left intact (and Chiang didn't forcefully dismantle it) would there still have been a civil war? What would the Republic of China likely look like in this case?