Introduction“No event in American history is more misunderstood than the Vietnam War.” (Richard M. Nixon, 1985) Despite nearly half a century of hindsight, numerous studies, and the declassification of military documents, former President Nixon's statement is still true. Of all the wars the United States fought in, the Vietnam War forced most Americans to ask themselves what we were fighting for and why. Was the Vietnam War a just war? Just War Theory Just war theory has been shaped over the centuries by historians and philosophers. However, the most systematic account of just war theory was formulated by St. Thomas Aquinas in his Summa Theologicae. According to just war theory, the moral reality of war is divided into two parts. Wars are judged twice, first by reference to the reasons nations have for fighting and second by reference to the means they adopt in actual combat. (Walzer, 21) The first sentence is defined as jus ad bellum, or war justice. The second sentence is called jus in bello, or justice in war. Jus ad bellum provides guidelines for evaluating whether a war is just or unjust while jus in bello outlines proper conduct in war. Jus ad bellum does not imply jus in bello. Likewise, jus in bello does not require jus ad bellum. It is possible for a just war to be fought unjustly, just as it is possible for an unjust war to be fought justly. The principles of jus ad bellum are having a just cause, being declared by competent authority, possessing the right intention, and having a reasonable chance of success. A war must meet all of these requirements to be considered a just war. The first and most important condition of the jus ad bel... middle of the paper... Lewy. America in Vietnam.New York: Oxford University Press, 1978.Herring, C. George. America's Longest War: The United States and Vietnam. New York: John Wiley & Sons, 1979. Herring, C. George. The Pentagon Papers: The Department of Defense's History of U.S. Decision-Making on Vietnam. Boston: John Wiley & Sons, 1971. Morgenthau, J. Hans. America's stake in Vietnam. New York: Oxford University Press, 1956. Pike, Douglas. Viet Cong: The Organization and Techniques of the National Liberation Front of South Vietnam. Cambridge: Harvard Press, 1966. Podhoretz, Norman. Because we were in Vietnam. New York: Simon and Schuster, 1982. Sullivan, P. Michael. The Vietnam War: A Study in the Making of American Policy. Lexington: The University Press of Kentucky, 1985. Walzer, Michael. Just and unjust wars. New York: Basic Books, 1977.