So these hypothetical guys fighting in the korean war, which took place in the 1950s, haven't heard of nuclear weapons, when two were used in 1945? I think you actually did hit your head pretty hard.
Most peope thought of it as the atom bomb as per the (fictional, cartoonish) very atomic! bomb in The 50 Fingers of Dr. Terwilliger in 1953.
The Korean War ended in 1953.
The nuclear age began with the Castle Bravo detonation in 1954, the extent of which would be classified for a while since it was far bigger than they estimated and ended up having to relocate some aboriginal islanders.
That said China was willing to throw tens of thousands of troopers to push the UN forces south. McArthur was even considering using atomic weapons to disrupt supply. In 1951 controlled territories stabilized at what would become the DMZ.
I totally understand you, Private. I recently dreamed of a nuclear bomb ending a world war, then everything using nuclear power and then a new war starting because of scarcity. That dream was weird but the floating ball shaped robots and the nuclear powered armor looked cool.