A Distant Mirror: The Calamitous 14th Century

by Barbara W. Tuchman

While desirable in any epoch, a “just war” in the 14th century was virtually a legal necessity as the basis for requisitioning feudal aids in men and money. It was equally essential for securing God on one’s side, for war was considered fundamentally an appeal to the arbitrament of God. A “just war” had to be one of public policy declared by the sovereign, and it had to be in a “just” cause—that is, directed against some “injustice” in the form of crime or fault on the part of the enemy. As formulated by the inescapable Thomas Aquinas, it required a third criterion: right intention on the part of the participants, but how this could be tested, the great expounder did not say. Even more convenient than the help of God was the “right of spoil”—in practice, pillage—that accompanied a just war. It rested on the theory that the enemy, being “unjust,” had no right to property, and that booty was the due reward for risk of life in a just cause.