More than once, T. R. Fehrenbach notes (in This Kind of War), the world has seen an American army rise from its own ashes, reorient itself, and grow hard, bitter, knowledgeable, disciplined, and tough:
They had learned the Chinese could be cunning, but also stupid. Failing to meet quick success, he could not change his plan. Often he continued an operation long after it had turned into disaster, wasting thousands of his troops. Lacking air cover, artillery, and armor, his hordes of riflemen could be — and were — slaughtered, as the Eighth Army learned to roll with the punches and to strike back hard.
Again and again, with the prodigal use of men, he could crack the U.N. line at a given point. But the men at the point had learned to hold, inflicting terrible losses, and even if the line gave, the Chinese could not exploit, while U.N. reinforcements, mechanized, rushed to deploy in front of them and to their flanks.
In the terrain of South Korea, battle was more open, and in open battle no amount of savage cunning could substitute for firepower.
Subsequent to the failure of the Chinese Spring Offensive [1951] the UN went on the offensive and the Chinese began to surrender in large numbers en masse, platoon, company and even battalion.
At that moment the Chinese called for a truce and armistice talks which were almost instantly agreed to by the UN command.
The Chinese were far from invincible. They were getting beaten and they knew it.