In ancient Rome, a "just cause" for war might include the necessity of repelling an invasion, or retaliation for pillaging or a breach of treaty.Livy 9.1.10; Cicero, Divinatio in Caecilium 63; De provinciis consularibus 4; Ad Atticum VII 14, 3; IX 19, 1; Pro rege Deiotauro 13; De officiis I 36; Philippicae XI 37; XIII 35; De re publica II 31; III 35; Isidore of Seville, Origines XVIII 1, 2; Modestinus, Libro I regolarum = Digesta I 3, 40; E. Badian, Roman Imperialism in the Late Republic (Ithaca 1968, 2nd ed.), p.11. War was always potentially nefas ("wrong, forbidden"), and risked religious pollution and divine disfavor.William Warde Fowler, The Roman Festivals of the Period of the Republic (London 1925), pp. 33ff.; M. Kaser, Das altroemische Ius (Goettingen 1949), pp. 22ff; P. Catalano, Linee del sistema sovrannazionale romano (Torino 1965), pp. 14ff.; W. V. Harris, War and imperialism in Republican Rome, 327-70 B.C. (Oxford 1979), pp. 161 ff. A "just war" (bellum iustum) thus required a ritualized declaration by the fetial priests.Livy 1.32; 31.8.3; 36.3.9 More broadly, conventions of war and treaty-making were part of the ius gentium, the "law of nations", the customary moral obligations regarded as innate and universal to human beings.Cicero, De officiis 3.17.69; Marcia L. Colish, The Stoic Tradition from Antiquity to the Early Middle Ages (Brill, 1980), p. 150.
In ancient Rome, a "just cause" for war might include the necessity of repelling an invasion, or retaliation for pillaging or a breach of treaty.Livy 9.1.10; Cicero, Divinatio in Caecilium 63; De provinciis consularibus 4; Ad Attic?um VII 14, 3; IX 19, 1; Pro rege Deiotauro 13; De officiis I 36; Philippicae XI 37; XIII 35; De re publica II 31; III 35; Isidore of Seville, Origines XVIII 1, 2; Modestinus, Libro I regolarum = Digesta I 3, 40; E. Badian, Roman Imperialism in the Late Republic (Ithaca 1968, 2nd ed.), p.11. War was always potentially nefas ("wrong, forbidden"), and risked religious pollution and divine disfavor.William Warde Fowler, The Roman Festivals of the Period of the Republic (London 1925), pp. 33ff.; M. Kaser, Das altroemische Ius (Goettingen 1949), pp. 22ff; P. Catalano, Linee del sistema sovrannazionale romano (Torino 1965), pp. 14ff.; W. V. Harris, War and imperialism in Republican Rome, 327-70 B.C. (Oxford 1979), pp. 161 ff. A "just war" (bellum iustum) thus required a ritualized declaration by the fetial priests.Livy 1.32; 31.8.3; 36.3.9 More broadly, conventions of war and treaty-making were part of the ius gentium, the "law of nations", the customary moral obligations regarded as innate and universal to human beings.Cicero, De officiis 3.17.69; Marcia L. Colish, The Stoic Tradition from Antiquity to the Early Middle Ages (Brill, 1980), p. 150.