 They were wrong. What happened was the Chinese sent something like 300,000 troops across the Yalu River to engage the UN forces, most of whom were American soldiers, Army and Marines. And the 1st Marine Division, some of its forces were down in a place called Haguru-ri, which was south of the Chosin Reservoir, and where the UN forces were setting up a perimeter that presumably would stop the Chinese from getting any further.