Yeah, China repeatedly told UN army not to cross the 38th parallel as the UN mandate was supposed to be, otherwise China would intervene, but, US ignored Chinese warnings. calling China bluffing and thought Chinese army would not dare to intervene becos it was too weak in US eyes.If US didn't cross the 38th parallel, there would be no Chinese intervention.
If US army weapons were bad at The Battle of Chosin Reservoir as some claim, one just has to think how primitive and infinitely worse the weapons the Chinese army had at hands, Chinese army at the battle were not even wearing winter clothes designed for the winter conditions in North Korea but were in light wears suited for South China since that's where those Chinese troops were dispatched to Korea. One company of Chinese soldiers at The Battle of Chosin Reservoir were all frozen to death while engaging in ambush. The disparity of the fire power between US army and Chinese army in Korean war is just mind boggling. Chinese army at The Battle of Chosin Reservoir had no air and naval support at all.