The Evolution of Law of War

Abstract

It is generally concluded that since time immemorial war may have existed, but the nature of war is nonetheless an issue that continues to perplex humankind. In ancient times, each state had its own theories and perceptions of how the nature of war should be defined. For example, in ancient Greece, ‘waging war against barbarians is considered just’.1 It was Saint Augustine (354–430 A.D.), a representative Christian figure in ancient Rome, and Saint Thomas Aquinas (1225–1274 A.D.), renowned Medieval theologian, who first put forward just war doctrine. To their mind there were so-called ‘three principles’ that govern the prerequisites for the initiation of war, namely, the authoritativeness of the initiator of war, just reasons for waging war, and the legitimate intentions of war.2 Hugo Grotius later expanded upon the concept of just war, and it eventually became one of the sources of modern law of war. Inspired by natural law and elaborated upon by theologians, just war doctrine consistently held prestige within French legal writings, and when the 16th century ended, it was codified by Spanish jurists such as Francisco de Vitoria and Francisco Suárez. Just war doctrine regards war as neither a fortuitous event nor a simplistic fact, but a procedure through which to resolve international conflict. A just war must accord with four conditions: (1) in the name of justice—that is, a war can only be waged by a legitimate public authority, consequently private wars in the Middle Ages were condemned; (2) a just cause—that is, a reason predicated upon what is just, but also justifies the damages caused by war; (3) necessity—there are no other means by which justice can be achieved; and (4) appropriate conduct—that is, war must be conducted in a manner appropriate for the renewed restoration of order and peace.3