Just Wars and the Roman Empire

"The earliest mention of distinction between 'just war' (bellum justum) and 'unjust war' (bellum injustum) can be traced back to the Roman Empire. As long as the Roman Emperors had not embraced Christianity, the Church upheld a pacifistic posture and even forbade Christians to enlist as soldiers. After Christianity had become the official religion of the Roman Empire in the days of Constantine, the Church was compelled to modify its view about war. From that point onwards, the Christians were required to shed their blood for the Empire. The Church had to find a moral ground for this change and this was done by Saint Augustine. He enunciated that every war was a lamentable phenomenon, but the wrong suffered at the hands of the enemy imposed 'the necessity of waging just wars'. This was later refined by Saint Thomas Aquinas."