Fei teng de qun shan

The effect of Cultural Revolution (1966 - 1976) is clearly seen here:

The important fact the movie excludes is that as much as 300,000 Nationalist troops in Shandong Province fighting the communist were ex-communists, and the reason they were forced to join Nationalists was because the political purges simply due to these ex-communists' family background: they did not came from the impoverished peasantry, but from middle, upper middle peasantry, or landlord class. These Chinese patriots joined communist to fight fascist Japanese aggressors, and proved themselves in the battles, but their loyalty were in doubt after the end of the second World War when communists and nationalists begun to fight each other.

This tragedy was openly admitted by Mao as a big mistake, but due to the political atmosphere of Cultural Revolution era, the film crew dared not to include it in the film.