So I love history and have read every book on the Korean war. This is obviously a movie to build patriotism and paint China's participation in the Korean war in a good light. Of course there is some truth in the movie. The Chinese fought bravely and against terrible odds but here are a few historical errors.
1) North Korean started the war when it invaded South Korea.
2) The US and UN had no intention of invading China.
3) The Chinese troops were not volunteers. They were conscripts.
4) The Chinese troops were very poorly armed and dressed. Most wore sneakers.
5) The US/UN was surprised by the initial attack and retreated.
6) China took Seoul but were later pushed back
7) There was no winner in this war. Everyone lost
8) North Korea is one of the poorest countries in the world. China's support of North Korean has caused the death and suffering of millions of North Koreans
9) Mao's son did not die trying to get a map. He was either cooking eggs or sleeping late and failed to get out of the building before it was bombed. These versions are from Chinese sources who were with him