[13] In the early centuries of our era Christians seem to have occasionally refused to serve in the army from religious scruples. But soldiers were not always required to change their profession after baptism. And in _Acts_ X., for example, nothing is said to indicate that the centurion, Cornelius, would have to leave the Roman army. See Tertullian: _De Corona_ (Anti-Nicene Christian Library), p. 348. The doctrine of the Church developed early in the opposite direction. It was its fighting spirit and not a love of peace that made Christianity a state religion under Constantine. Nor was Augustine the first of the Church Fathers to regard military service as permissible. To come to a later time, this change of attitude has been ascribed partly to the rise of Mahometan power and the wave of fanaticism which broke over Europe. To destroy these unbelievers with fire and sword was regarded as a deed of piety pleasing to God. Hence the wars of the Crusades against the infidel were holy wars, and appear as a new element in the history of civilisation. The nations of ancient times had known only civil and foreign war.[14] They had rebelled at home, and they had fought mainly for material interests abroad. In the Middle Ages there were, besides, religious wars and, with the rise of Feudalism, private war:[15] among all the powers of the Dark Ages and for centuries later, none was more aggressive than the Catholic Church, nor a more active and untiring defender of its rights and claims, spiritual or temporal. It was in some respects a more warlike institution than the states of Greece and Rome. It struggled through centuries with the Emperor:[16] it pronounced its ban against disobedient states and disloyal cities: it pursued with its vengeance each heretical or rebellious prince: unmindful of its early traditions about peace, it showed in every crisis a fiercely military spirit.[17] [14] There were so-called “Sacred Wars” in Greece, but these were due mainly to disputes caused by the Amphictyonic League. They were not religious, in the sense in which we apply the epithet to the Thirty Years’ war. [15] “The administration of justice among rude illiterate people, was not so accurate, or decisive, or uniform, as to induce men to submit implicitly to its determinations. Every offended baron buckled on his armour, and sought redress at the head of his vassals. His adversary met him in like hostile array. Neither of them appealed to impotent laws which could afford them no protection. Neither of them would submit points, in which their honour and their passions were warmly interested, to the slow determination of a judicial inquiry. Both trusted to their swords for the decision of the contest.” Robertson’s _History of Charles V._, (_Works_, vol. V.) Sect. I., p. 38.