All those 1-star review bombs are exposing the current climate of McCarthyist sinophobic hysteria in the west pretty accurately.
For anyone not suffering from McCarthyist hysteria, this is a decent movie with well-crafted, tense, and dramatic action scenes. It also does it's job of illustrating the theme of ordinary people being capable of extraordinary heroics feats and self-sacrifice when under existential threat.
Also, a good choice to feature Mao Anying's participation and death in the narrative. It showcases that the social class he was born in as Mao Zedong's son mattered nothing, because death is equal to all when fighting a war.
Less well done were the scenes of the American side. The directors and script writers did provide at least a couple of scenes of American soldiers talking about home life, and I thought this was a good choice to provide the American side with some humanity. But the actors were really chewing the scenery here, especially in their line delivery, which was unfortunate. I think, however, that this can mainly be attributed to the fact that these actors are far from being A-listers. Unfortunately, China still has not build up a decent pool of ethnically non-Asian quality actors, so I foresee more of this happening in the future.
Now a bit of historical context here on China's motives for partaking in this war:
A few decades before the Korean War, China had been brutally invaded by imperial Japan through the Korean peninsula, which started off the theater of WW2 in the Far East. Given that this history was still fresh in the minds of the Chinese at the time, China was very sensitive to any happenings on the Korean peninsula. For that reason, they warned the American side multiple times not to cross the 38th parallel or they would force China's hand. The Americans thought the Chinese were bluffing and crossed that line anyway. This (and the American fleets that had gone to the Taiwan Straits in the summer of 1950) convinced the Chinese that the USA would try to invade and colonize China after taking control of the Korean peninsula. To preemptively stop this threat, China decided to set up the People's Volunteer Army to defend against the existential threat.
