MacArthur wanted to Nuke the Chi-Coms back to the stoneage and was handstrung about the Chinese by Truman.
Which very likely may have ended up causing a US-Soviet nuclear exchange.
MacArthur is one of the most painfully overrated military leaders in US history. Like I said, prior to the controversy with Truman, he completely ignored large amounts of intelligence and warnings that Chicom troops were in North Korea in large numbers - and we ended up getting suprised, leading to the horrors of "Frozen Chosin" etc.
Just like he managed to lose his entire airforce in the Phillipines on the ground the day AFTER Pearl Harbor in World War II.