If Gen MacArthur....

If we had stopped

on the southern bank of the Yalu, we might have survived the attacks of the PLA. I think MacArthur could have handled that kind of conventional attack.

However, Bradley and Truman were taking into consideration a factor the Gneral ignored at America's peril. The Soviet Army in Europe. It occupied the Soviet Zones in both Germany and Austria. Moscow also had troops in Czechoslovakia. The US, British and French dforces were hollowed out in Europe. The Western Allies strength was in Korea. The Red Army wasn't all that strong at the time. But, it would have taken them much to cause problems if Moscow had decided to push west, if MacArthur had crossed the Yalu. Moscow may have gotten paranoid and moved anyway if MacArthur had even looked like he was going too far north.

MacArthur was so focused on Korea he ignored possible consequences of his actions in Europe. He forgot the speed of communications in 195x. Yes, it wasn't as fast as 2011. But, communications (UN crossed the Yalu) was a lot faster than it was in 1935. Dollars to dough nuts, if the UN had crossed the Yalu, by dawn in Germany, the Red Army would be marching west towards Paris.

 

Yes Truman had to fire Mac. It's the American way of war. Other than the advances in military and other technology, General Mac was fighting Korea like it was 1851 not 1951. In other words, he was fighting the war like it had no effect on other fronts. To him it was an updated version of the old colonial wars. China Gordon could have such an attitude. But Mac in 1951 couldn't.

Yes, I understand as a soldier on the line you only thought about the enemy in front of you. Mac on the other hand was a general of the army. IIRC, that's the equivalent of a Brit\Commonwealth field marshal. As a five star general, he got paid the big bucks to take such matters into consideration.
Stalin may have liked the idea of the PLA being sidetracked by the UN. However, if the UN had crossed the Yalu, he would have had no choice but to send elements of the Red Army west or make it look like it so the French and Brits would have pulled their troops back home.

 

In many ways, GEN Mac suffered in comparison to the generals coming out of the European Theater (Eisenhower, Bradley, and Patton). As Supreme Allied Commander, Eisenhower oversaw a much larger theater than DM, He had to juggle operations in Italy, Southern France, and the push from Normandy. Patton as stopped in front of Metz at the start of the Battle of the Bulge. When Ike recalled him and Bradley to Paris for a meeting concerning the German offensive, he had already ordered his staff to prepare plans for a left wheel drive to their north. His intel told him something was hinky about the German forces on their front. So when Ike and Bradley asked Patton when he could get his army moving north, Patton said right now and made the phone call to his headquarters.

He also suffered from serving under former subordinates:

Truman commanded a field artillery battery in France during WW1 under GM. He continued to actively serve in the Missouri National Guard. By Pearl Harbor, he was a LTC in the MoNG. He volunteered for active duty even though he was in the US Senate. Marshall told him he best served the Army by staying in the Senate. Suffice to say Harry S was not ignorant or unlearned in military affairs.

Bradley was a company and field grade officer during GM's tenure as Army Chief of Staff. At the time of the Korean War, Uncle Omar was the Chairman of the Joint Chiefs of Staff.

Ike was GM's AdC during the same period and followed GM in the same capacity after his retirement from the US Army to the Phillpines.

Suffice to say, GM had no professional friends when he needed them. Further, over the years he had done his best to antagonize them. Also, this wasn't the first time he had disobeyed Presidential orders. In 1932, President Hoover ordered him as Arny Chief of Staff to evict the Bonus Marchers from Washington, DC. He personally led the 12th Infantry Regiment, the 3rd Cavalry Regiment and six battle tanks on the streets of Washington in the action. Hoover ordered the gerneral not to follow the fleeing veterans and their families across the Anticostia River. GM disobeyed this direct order from his superior believing the Bonus Marchers were part of a Communist revolution rather than veterans assembling to petition their government. The marchers were evicted by cavalry charges, infantry bayonets and tear gas.