OSTILITÀ. — In the law of nations, this term denotes the use of coercive means against another State in order to bend its will and compel it to accept the desired solution to a question that could not or was not wished to be resolved through the ordinary channels. A hostile act does not in itself and invariably interrupt peaceful relations between the parties, unless it constitutes an expression of the intention to use it to bring about a state of war; modern international law therefore distinguishes between hostilities in peacetime and hostilities in wartime, or belligerent hostilities, toward which the parties themselves adopt different attitudes.
I. O. IN TIME OF PEACE. — With regard to the former, the most common doctrine, inspired by the canons of the positivist school, does not contest their lawfulness; indeed, it approves their use, on the basis of the general principle according to which the State would always and in every case be permitted to adopt those measures which it deems appropriate to defend its rights or assert its interests, provided that a positive norm of the international legal order does not prohibit it from doing so. Outside the provisions of that legal order, the State would retain its original freedom, and since the hostile act falls within this sphere, not being prohibited by any specific norm, it should be regarded as legally lawful, independently of the motives that give rise to II. To reinforce this theoretical argument, the existence of a customary norm, inferred from the conduct of States, is usually added: States, exercising full sovereign discretion, have always resorted to coercive methods. The theory thus formulated denies the existence of certain fundamental norms of justice, inherent in international society itself, which impose themselves by their intrinsic virtue upon the will of States and regulate all its manifestations, including the use of coercive means; and it elevates force not subject to law into the criterion of their relations, basing itself on a false conception of their original freedom, which can never be absolute, but is objectively and intrinsically limited. Woven into its fabric are legal voluntarism, which reduces all law to the positive expression of the will of States, and the more general concept of sovereignty, understood as a power limited only by law, itself established or accepted by that same will.
Catholic doctrine cannot accept these theoretical positions; but, proceeding from the principle that force, being in itself a means that is intrinsically neither good nor evil, cannot receive the seal of moral and legal legitimacy unless it is directed toward the attainment of an aim just in its essence, it likewise reaffirms, with regard to o. in time of peace, its position by declaring them lawful when they are placed at the service of law, for its defense or reparation, and unlawful in the contrary case. It does not, therefore, exclude the State’s power to resort to the use of violent means; it merely subordinates that power to the higher norms of natural justice and restricts its exercise within their bounds, rejecting the twofold axiom of voluntarism and unlimited sovereignty. Acts of o. which do not, merely by their adoption, interrupt ordinary relations are considered to include: retaliation, seizure, embargo, reprisals, and peaceful blockade.
Retaliation consists in opposing to an act contrary to law, interests, and equity an act that may be of the same kind, in order to compel a State to acknowledge its wrong and withdraw the measures it has adopted. Through seizure, a State takes possession of property belonging to another in order to extort reparation for a wrong suffered. An embargo is a special form of seizure whose object is the merchant vessels of the opposing State, and therefore excludes warships. With regard to reprisals, V. la voce corrispondente. Finally, blockade occurs when the opponent’s ports or strongholds are closed to all commerce, and it may therefore be maritime or continental. It is needless to point out that, in the use of these means, permitted by modern international law, the State must proceed cautiously, bearing in mind not only the most universal norms of justice, from which alone the lawfulness of its conduct can derive, but also the well-being of the international community and the possible complications detrimental to II. To this well-being, according to the principle already established by Vitoria with regard to war, even the defense of a certain right remains subordinate. In the case of retaliation and reprisals, moreover, every act contrary to the laws of humanity and to the most fundamental rights of the human person must again be deemed unlawful, even if undertaken by another State.
II. WARLIKE HOSTILITIES. — I. Beginning of hostilities. — For a long time, the practice prevailed of not beginning hostilities without having
(from V. JALABERT, LOUIS, Les Pontificaux mss. des Bibl. publ. de France, Paris 1937, pl. 163)
OSTIARIATO — Ordination of the porter: the handing over of the keys. Miniature from a Pontificale romano (late fifteenth century) — Lyon, Bibl. municip., ms. 5144, f. 119.
This principle, derived from a moral conception of war, was adopted by the Hague Conference of 1907, which, in Article 1 of Convention III, provided that hostilities were not to be begun by the contracting powers without a prior and unequivocal notice, either in the form of a reasoned declaration of war or in that of an ultimatum with a conditional declaration of war. The same convention, however, neither requires nor determines that an interval must elapse between notification and the beginning of hostilities, since the attempts of certain delegations to establish a minimum period of twenty-four hours had failed. Exceptions to the aforementioned rule have become so numerous, particularly after its acceptance, as to suggest that States do not feel themselves bound by it as they should, setting against it a contrary custom, condemnable for higher reasons of morality and justice. The commission of hostile acts expressing the will to establish a state of war, even when not preceded by any warning or declaration, in every case brings peaceful relations to an end, suspending the ordinary law governing them, and gives rise to the particular relationship of belligerency, bringing into force a new category of norms by which the conduct of hostilities is governed throughout the war.
2. Conduct of hostilities. — At the present time there are not a few political, or apparently juridical, theories that uphold the complete freedom of States in using offensive means against the adversary in order rapidly to break his resistance. It has been asserted that war, essentially inhuman, cannot be humanized, and even that the most humane war would be one which, by implacable methods, shortens the duration of the struggle, breaking the enemy’s strength more rapidly. It has additionally been argued from the juridical standpoint that, since war is a complex of hostile acts outside and contrary to the law in force among States, it cannot in itself be subject to law and therefore falls within that sphere of unregulated freedom where everything is permitted. A relationship of force, awaiting regulation by force, can have no criterion other than force itself, which must be left free to exert its pressure upon the adversary by every means at its disposal.
The theses just mentioned, which are connected with conceptual positions (for which V. GUERRA), have as their common foundation the amorality of armed struggle and the cult of force as the generator of law, and cannot be accepted by Catholic doctrine, which firmly rejects them. War is not the unleashing of cosmic forces or of the biological instincts of the species, as it has been defined, but a struggle between human beings and therefore entails a series of human acts which, like all other human acts, are subject to the laws of morality, justice, and humanity. Moreover, war is in itself an exercise of force that derives its justification from an end—the defense and reparation of a threatened or violated right—and therefore it is from that same end that the limits within which hostilities must be confined derive. This teleological principle, implicitly enunciated by Vitoria when he affirms that in a just war one has the right to do whatever is necessary for the defense of the common good, was consistently applied to the conduct of hostilities by the subsequent Catholic tradition, by Suárez, Molina, and other later authors.
Associated with it was the distinction, with regard to the power to inflict harm, between nocentes and innocentes, that is, between combatants and non-combatants, together with the moral and juridical rule that the latter should be spared direct attack. Thus a principle of humanity was made to prevail over the use of force, first imposed in practice by the ecclesiastical authorities in the “Peace of God,” and later theorized as the source of a moral obligation. The foundations, therefore, upon which Catholic thought based its doctrine concerning the conduct of hostilities are: the distinction between lawful and unlawful means of attack, deduced from the teleological criterion of war; and that between combatants and non-combatants, derived from the principle itself and from the laws of humanity; subordinately, there was added the principle of loyalty, already mentioned by St. Thomas (Sum. Theol., 2ᵃ-2ᵃᵉ, q. 40, a. 3), who excluded the lawfulness, in wartime, of deceiving the enemy by asserting falsehoods and failing to keep promises, since there exist «quedam iura bellorum, et foedera etiam inter ipsos hostes servanda».
The practical consequences of these principles concerning what is lawful or unlawful in the conduct of hostilities are straightforward and evident. They were systematically deduced better than by anyone else by Taparelli. The purpose of war, he says, consists in bringing the enemy back to order by force; consequently, whatever cannot offer resistance must not be destroyed. Thus all vandalism, the useless destruction of houses and property, and the indiscriminate slaughter of the old, women, and children are condemned. Every harm not necessary to break the enemy’s strength is forbidden in humane warfare by the very purpose of war. The same law of avoiding unnecessary harm forbids among nations the use of certain offensive means whose effects could not be controlled by directing their damage against the forces of resistance. Spreading contagion, poisoning waters, and other similar chemical or bacteriological means must be understood as prohibited. The same Taparelli adds: if it is forbidden to inflict unnecessary harm, all the more is it forbidden to inflict moral harm. Treachery, perjury, parri-
cide or sacrilege must not occur in war among men, and the sanctity of truces and armistices, respect for the dead, humane treatment of the wounded, discretion in requisitioning provisions, and so forth must be observed. The uncertainties regarding certain methods of warfare, still admitted as lawful by medieval authors and those of the sixteenth century under the pressure of the rough customs then prevailing, came to an end in Taparelli’s more mature elaboration, which had by then become the common doctrine of Catholic thought.
3. Positive law and o. — Positive international law has accepted the principles set forth above and their practical consequences. In various conventions, the States have gradually expanded the code of the laws of war, so as to mitigate substantially, at least in the texts of the agreements, the harshness of o. In this regard, the following should be recalled in chronological order: the Geneva Convention of 1864 for the improvement of the condition of wounded military personnel; the Declaration of St. Petersburg of 1868 excluding the use of explosive projectiles; the various Hague Conventions of 1899, 1904, and 1907 concerning the laws and customs of war on land and at sea; the Geneva Convention of 1906 for assistance to the sick and wounded; the Washington Treaty of 1922 for the protection of the lives of neutrals and non-combatants and for the prohibition of the use of asphyxiating gases and chemical means; the Geneva Protocol of 1925 concerning the prohibition of asphyxiating and toxic gases and bacteriological means; and finally the Geneva Convention of 1929 for the improvement of the condition of the wounded, the sick, and prisoners.
The outline just given of the numerous international conventions shows how positive law has progressed, particularly during the last century, adapting itself to the higher demands of natural justice and to the laws of humanity. Without descending to particular determinations, a consideration of its general lines will suffice to make this progress clear. The principle enunciated in art. 23 of the Hague Regulations of 1907 must be regarded as a norm accepted by the majority of States: belligerents do not possess an unlimited right in the choice of means of attack. Their right is circumscribed both by the aims pursued by the war, which exclude unnecessarily cruel means, and by the laws of humanity. This criterion, explicitly mentioned in the preamble to the St. Petersburg Convention of 1868, informs all the positive provisions concerning the conduct of o. Moreover, the distinction between combatants and non-combatants, with the consequent prohibition against directly harming the latter, must still be regarded as a norm of contemporary international law of war. It should further be noted that not a few articles of the Hague Convention of 1907 sanction the obligation of good faith, prohibiting all methods capable of deceiving the enemy and not reducible to a military stratagem.
With regard to means of attack, the Regulations annexed to the Convention just mentioned prohibit the use of poison and poisoned weapons. This provision must be supplemented by the Second Hague Declaration of 1899, which prohibits projectiles that spread asphyxiating and deleterious gases, a prohibition reaffirmed by the Washington Convention of 1922. There follows the prohibition against killing or causing to be killed treacherously individuals belonging to the enemy State; against killing or wounding an enemy no longer capable of defending himself or who has surrendered at discretion; and against employing weapons and projectiles capable of causing superfluous injury. Particular provisions regulate the treatment of the wounded, the sick, and prisoners of war, and the latter may not be put to death.
The use of stratagems is not prohibited; nevertheless, the Hague Regulations of 1907 expressly prohibit the improper use of the white flag, the flags and uniforms of the enemy, and the distinctive emblems of the Red Cross, as well as all methods constituting acts of perfidy or contrary to military honor. The issuance of an order to give no quarter is likewise prohibited, although certain particular legislations admit it in cases of necessity, making it a convenient means of evading the peremptory prescriptions of the law. Necessity can never legitimize the violation of the norms of justice and humanity.
4. The Church and the conduct of o. — The provisions of positive international law briefly described above derive from the Christian tradition, which, through the ecclesiastical hierarchy, worked to soften the customs of war.
The movement in favor of a greater sense of humanity in the conduct of o. began in the Middle Ages in France, where several local and regional councils issued prescriptions on the matter. The Council of Narbonne in 990, for example, threatened with excommunication all those who attacked the Cluniac cenobites and took other measures to restrain o. (Hefele-Leclercq, IV, pp. 869–70 and 869 note 2). In 989, measures in favor of combatants had already been extended by the Council of Charroux near Poitiers from ecclesiastics and Church property to peasants and the poor, excommunicating anyone who deprived them of their goods, as well as to travelers and merchants (loc. cit.). Under the auspices of the Church, around 997 a league for the maintenance of peace was created, in which laymen participated with deliberative functions and were obliged to assist the bishop in suppressing acts of violence committed within his territory (loc. cit.). It was later transformed, in 1908, into a compulsory peace association, in which all men from the age of fifteen were required to enlist and take an oath. The Holy See did not fail to promote the « peace of God »; from as early as 1930, the legates of Pope Giovanni XIX went from council to council to impose it and anathematize transgressors (ibid., p. 960 sgg.).
The « truces of God » also contributed to the softening of the customs of war. The Council of Elne in 1027 (ibid., p. 969 sg.), after confirming the protective provisions for clerics, monks, and women, determined that from none o’clock on Saturday until the early hours of Monday everyone was forbidden to attack his enemy. The truce of God, initially a simple application of the precept of festal rest, was extended also to other days and to particular liturgical seasons, such as Advent and Lent. A legate of Pope Alessandro II introduced it into Spain in 1068; two councils introduced it into Italy, those of Melfi in 1089 and Troia in 1099 (ibid., V, pp. 345 sgg., 371 sgg.). In 1095, Urbano II, present at the Council of Clermont, wished to extend the institutions of peace to the entire Church in view of the Crusade. The Peace of God and the Truce of God were confirmed by Pasquale II (1107) and by Callistus (1119, ibid., V, p. 581 sgg.).
With respect to the use of means of attack, Innocenzo II at the Lateran Council of 1139 prohibited the employment of ballistae and arrows. In 1179, Alessandro III renewed the prescription that priests, clerics, monks, lay brothers, pilgrims, merchants, peasants traveling or engaged in agriculture, and their animals should enjoy appropriate security. These prohibitions and prescriptions were renewed by Innocenzo III (ibid., V, pp. 728–29, 1103). The Church also exercised a beneficial influence on the customs of war through the institution of chivalry and through the Third Orders.
It is today a common view among historians of international law that the laws governing the conduct of o. in particular derive from the Church’s constant effort. The Church succeeded in introducing into the still savage souls of peoples certain principles of humanity which, later developed theoretically by the first Catholic systematizers of international law, have become the inheritance of civilized nations, as part of modern positive law.
(da L. Amundsen, Greek ostrakon in the University of Michigan collection, Londra 1933, (av. 1, n. 13))