Haig was the aide-de-camp to General Edward "Ned" Almond, a MacArthur pet and commander of X Corps during the early part of the war. He was in the room when MacArthur and Almond were discussing the then-proposed landing at Inchon with the Joint Chiefs of Staff. This quote from his autobiography is worth remembering, IMO:
"I realized that I had witnessed something that would go down in history, a Cincinnatian act of moral courage. Some years passed before I fully understood the lesson it contained; that when you are in a position of trust and a course you know to be right is questioned for political reasons, you must act on your own convictions based on your own experience, because that is your duty to the American people. It was not vainglory but wisdom that motivated MacArthur. He believed that the Inchon landing would succeed, and that it would save 100,000 lives. As events were to prove, he was right when everyone else was wrong."
He was also one of the few people who truly understood terrorism very early on, partially because he was the target of a terrorist attack when he was NATO commander.