The roots of modern international law come from one specific strand of thought emerging out of antiquity: the Christian Roman Empire that took shape after the conversion to Christianity of the Emperor Constantine in the year 312 AD. Although there were important ideas of restraint in war in pre-Christian Greek and Roman thought and indeed in cultures all over the world, it is the blend of Christian and Greco-Roman thought that set the context of the development of full-blown just war thinking over a period of centuries.
Christianity before this time had been suspicious of entanglement in the affairs of the Empire. For the first several centuries of the movement, Christians interpreted the teaching of Jesus in the Sermon on the Mount and other places quite literally, and saw themselves as committed to pacifism (the refusal to use force or violence in all circumstances). Although many appreciated the relative peace, prosperity, and ease of travel the Empire’s military force made possible, Christians felt prayer on behalf of the Emperor was the limit of their direct support for it.
Much changed with Constantine.
This was part of my reading for Air Command & Staff College, my professional military education, excerpted from “Ethical Issues in War: An Overview,” by Martin L. Cook, originally published by the Strategic Studies Institute in U.S. Army War College Guide to National Security Policy and Strategy, 2d Edition, Chapter 3, June 2006.
“Much changed with Constantine.” So the question I ask is, were those changes good? On the one hand, Christians were no longer being eaten by lions on a regular basis as entertainment for Roman citizens. On the other hand, is it right for Christ-followers to accept a “blend of Christian and Greco-Roman thought?” When you blend these thought patterns, do you lose something of the pure Christian thought mode? Dangerous questions, I think.