After World War II, these forces of former Japanese puppet regimes once again returned to the nationalist camp for the same reason they defected to the Japanese invaders. Obviously, it was difficult for Chiang to immediately get rid of these warlords for good as soon as they surrendered to Chiang and rejoined the nationalists, because such a move would have alienated other factions within the nationalist ranks, and these former Japanese puppet regime's warlords could still help the nationalists to gain more territories by holding on to what was under their control until Chiang completed the deployment of his own troops to take over.
After World War II, these forces of former Japanese puppet regimes returned to the nationalist camp again for the same reason they had defected to the Japanese invaders. Clearly, it was challenging for Chiang to swiftly eliminate these warlords completely once they surrendered and rejoined the nationalists because such an action would have estranged other factions within the nationalist ranks, and these former Japanese puppet regime's warlords could still assist the nationalists in gaining more territories by maintaining control over what they had previously managed until Chiang deployed his own troops.