The Chinese had high levels spies and knew in advance that Truman would not use nukes. If Truman had been chomping at the bit to send a bunch of Communists to Thermonuclear Hell there would only be one Korea today.
I hope Michael Caine is interviewed about this film. Caine is an interesting guy and, while I gather his politics are largely MovieWorld liberal, he is capable of being quite heterodox from time to time. As a young man, he was a working class yute with vaguely pro-communist views. Then he got called up for military service (1952-54), which is how he found himself sitting in a foxhole in Korea, behind a machine gun, watching Chinese human wave attacks roll up the hill towards him. Apparently he was in a couple of situations in which he gave himself up for dead. He altered his views somewhat, as he realized that there was something wrong with a system that had such complete contempt for human life.
My brother-in-law was there when the Chinese came across the border.
The first wave had rifles. The second wave had ammo and were to pick up the rifles of the killed first wave. The third wave had what ever tool they could find. Some had staves and rocks. Some had nothing.
China had so many excess males they found a good way to get rid of them in Korea.
He walked across Korea back and forth several times. When they finally got relieved and put on a ship back to the US via Africa and Europe, every port of call made he refused to get off the ship till back in the USA.