Stoney G. answered 03/25/21
Long time History Buff
When GEN MacArthur threatened to escalate the war in Korea by implicating China, he did so outside of his authority and violated the relationship between political and military leaders in the conduct of war. MacArthur, a veteran of WWII viewed the situation through that lens and had not fully accepted that Korea was in fact a limited war with limited objectives. By retaliating against China he would have been expanding the war objectives beyond what they were supposed to be as well as potentially initiating a third world war, one in which a post-WWII American military was not equipped to fight. If Truman had acquiesced and allowed MacArthur to pursue his own ends, he would have been no better than the heads of state in WWI by abdicating his responsibilities for the conduct of the war. Finally, Mac Arthur's ends were extreme and in addition to bringing the war to China, he suggested using nuclear weapons against the Chinese as well as along the entirety of the Yalu river.