Good comments, all. I wanted to add some things Toland makes clear that I think many Americans are not aware of.
First, the Chosin Resevoir was a MacArthur fiasco, pure and simple. Intelligence reports had indicated for some time that several hundred thousand Chinese troops had amassed south of the Yalu River prior to the move along the resevoir. MacArthur had placed the Marines under operational control of General Nate Almond, one of his cronies, who had limited experience, and, as it turns out, ability. He also thought the intelligence reports a joke, which led to the tragedy of Chosin. While Puller gets a lot of press for Chosin (I am not in any way denigrating his contribution), Toland points out in some detail that Cols. Faith and Taplett were the real heroes in the breakout. Faith was killed when his column stalled and Taplett lived to be rotated home.
Second, General Walker gets little credit for his control of the 8th Army. However, his retreat was handled with such competence that historians now believe he prevented a second disaster equal in magnitude to the Pusan Perimeter simply by the way he moved his divisions to allow reinforcing actions, and to protect against gaps and ROK soldiers bugging out. Walker was against the Inchon landing and believed his plan to cut Korea at Kunsan in the east allowed for much better logistics and combat control.
Third, this was the first time that experienced combat officers were rotated home en masse so that inexperienced commanders could get their "ticket" punched for further promotion. This practice reached catastrophic proportions in Viet Nam. General Hal Moore was the first high ranking official to publicly criticize this process (after his retirement), which led to the death of many soldiers in Korea and later, Viet Nam. For reference, read his book: "We Were Soldiers Once, And Young", which details the battle at Chupong Massiff and the first large scale loss of American troops in the RVN.
Fourth, Imposter is right on the money about the ROK allies. They constantly ran when under heavy fire forcing U.N. (read American) divisions to shore up gaps in the lines and prevent catastrophe. A lot of American boys were lost because of the cowardice and poor leadership among the ROK troops.
Finally, this war was largely fought from Washington, which as we learned again a dozen years later, leads to disaster. The country was unprepared for the war, it was highly unpopular and the politicians were unwilling to commit the resources needed at key points during the conflict. They also failed to understand that this war was being fought by Mao from China and that Kim Il Sung had little real control. Mao was prepared to lose hundreds of thousands of his troops to embarrass the U.S. and guessed correctly that the U.S. government would never consider using atomic arms. That left him, realistically, in total control of the war.