MacArthur publicly complained to President Truman's decisions. He even publicly accused Truman of "appeasement" regarding China, which infuriated Truman. The tensions arose more between the two. As the leader of the UN forces, MacArthur opted to pursue North Korea his way. Truman was concerned about the Chinese army joining into the war, and he told MacArthur not to go near the Chinese border. MacArthur decided to cross the border anyway.
Hope this helps though it may not be much info...