To what extend did the various KMT/Nationalist-aligned factions cooperate and consolidate themselves in the lead up to and during the Second Sino-Japanese War?

[evanharder101]

I have played a lot of Hearts of Iron 4 in the past, and the way in which the game breaks up China got me thinking: did the various warlord factions (outside of the communists) actually separately control their territories and policies just before and during the war with Japan, or were they all brought under the full control of Chiang Kai-Shek? What was the internal political and military control of the Nationalist faction like?