I want to know the answer to the following question:
When did cooperation between communist and nationalist forces end?
All the background I'm provided with is that "However, its policies of brutality toward the Chinese population, of not yielding any real power to these regimes, and of supporting several rival governments failed to make any of them a viable alternative to the Nationalist government led by Chiang Kai-shek.". Is that enough to answer the question?
Answer: no