In Korea, MacArthur was mostly responsible for the utter CATASTROPHE that befell the 8th Army, particularly the near destruction of the 2nd Infantry Division at Kunu-Ri, and the annihillation of Task Force McLean/Faith east of the Chosen Resovoir, as well as the 80 mile withdrawal of X Corp. He utterly ignored the solid intelligence of the build-up of NINE CCF Armies consisting of 300,000 men, who had crossed the Yalu River, routed the ROK 6th and 8th Divisions, cut the US 8th Cavalry Regiment to pieces at Unsan, roughed up the 5th Cav, forced the 24th Division to break off an attack, and mauled the Brit Commonwealth Brigade.
This was largely due to his ego, and a single minded myopic focus on advancing to the Yalu at the expense of prudent military caution. He was a great commander, but some of his personality quirks resulted in near disaster on many occasions.
There are a lot of things a lot of people know which are not so.
The French purposely let themselves get surrounded by truly massive North Vietnamese forces knowing that America had promised to use nuclear weapons to kill all the NV at one time.
A U.S. Senator, Lyndon Johnson found out about it and forced the issue. The U.S. would not use the weapons and the French who fought as well as soldiers ever fought were all killed or captured.