I'm going from memory. MacArthur had the Koreans on the run?
The Chinese took about ten divisions and sent them across the frozen over river.
We just shelled the river. Chinese were all gone by next morning..
MacArthur did have the Norks on the run and penned up in a small corner near Vladivostok. The Chinese massed their army in an area lightly defended by UN troops and when they attacked in mass human wave attacks at night, they soon overwhelmed the few troops stationed in that area. They now threatened MacArthur's flank and forced him to retreat. A lack of sufficient ground support aircraft allowed the Chinese to make fast headway, albeit with very heavy casualties, and the UN troops retreated back south of Seoul.
After Ridgeway took command, the started driving the Chinese back north to about the 38th parallel using what General Ridgeway called "meat grinder" tactics that used US superiority in artillery and aircraft to grind down the numerically superior Chinese before driving them out of an area. Truman then directed Ridgeway not to cross the 38th parallel and did not increase troop levels by what was needed to finish driving the Chinese back across the Yalu river. The stalemate ground on for another 18 months or so before the truce took effect in 1953.
It is estimated the Chinese suffered close to a million casualties in their close to 2 years in the war.
