We're not going to get into exhausting detail about the civil war, but spoiler alert, the communists won. There are a few things to point out. First, even though Mao emerged victorious, he and the communists were almost wiped out in 1934, except that they made a miraculous and harrowing escape, trekking from southern China to the mountains in the north in what has become famously known as the Long March, a great example of historians missing an opportunity since it could easily have been called the Long Ass March as it featured donkeys. And second, for much of the time that Guomindang was trying to crush the CCP, significant portions of China were being occupied and or invaded by Japan. Thirdly, the communists were just better at fighting the Japanese than the nationalists were, in spite of the fact that Chiang Kai-shek had extensive support from the US. And each time the nationalists failed against the Japanese, their prestige among their fellow Chinese diminished. And it wasn't helped by nationalist corruption or the collection of onerous taxes from peasants or stories about nationalist troops putting on civilian clothing and abandoning the city of Nanking during its awful destruction by the Japanese army in 1937.