[That was my war - Korean - and we could have driven them back to the other side of the Yalu but the UN was insistent we were to hold at the 38th parallel.
You can’t win a war playing defense.]
I think neither Truman nor Eisenhower wanted to pay the price in men necessary to drive the Chinese back to the Yalu River. So they settled for half a loaf. In so doing, they set the stage for the losses of the Vietnam War. IMHO, if they had unified the Korean peninsula and smashed the Chinese armies squatting there, the Communist Party’s position in China would have been far less secure, and local counter-revolutionary activity would have had some chance of succeeding, in conjunction with a Nationalist push across the Formosa Strait. Which might have strangled the Vietnam War in its cradle, given the Viet Minh’s reliance on Chinese supplies for its war against the French. No North Vietnam, no Vietnam War.
your point is well taken. And as to “pay the price in men necessary” in driving them off the peninsula, we paid a heavy price keeping the 38th. The Chinese and Nk forces kept trying to move the line south.