HOSTILITY. - In the law of nations this term designates the use of coercive means against another State, in order to bend its will and make it accept the desired solution of a question that could not or would not be resolved through the ordinary channels. A hostile act does not in itself and always interrupt peaceful relations between the contending parties, unless it is the manifestation of the will to provoke a state of war by it, and for this reason modern international law distinguishes hostility in time of peace and hostility in time of war or belligerent hostilities, in regard to which the contending parties themselves adopt a different attitude.
I. HOSTILITY IN TIME OF PEACE
With regard to the former, the most common doctrine, inspired by the canons of the positive school, does not contest their lawfulness; indeed it approves their use, basing itself on the general principle according to which it would always and in every case be permitted to the State to adopt those measures which it deems opportune for defending its own rights or for asserting its own interests, provided that a positive norm of the international order does not forbid it. Outside the provisions of such an order the State would retain its original freedom, and since the hostile act falls within this sphere, not being forbidden by any specific norm, it should be regarded as a juridical licit act, independently of the motives that provoke it. To reinforce this theoretical argument there is usually added the existence of a customary norm, deduced from the conduct of States, which with full sovereign discretion have always had recourse to the coercive method. The theory thus formulated disregards the existence of certain fundamental norms of justice, immanent in international society itself, which impose themselves by their own intrinsic virtue upon the will of States and regulate all its manifestations, including the use of coercive means; and it elevates to the criterion of their relations force not subjected to law, basing itself upon a false conception of their original freedom, which can never be absolute, but is objectively and intrinsically limited. Among its threads there operate juridical voluntarism, which reduces all law to a positive expression of the will of States, and the more general concept of sovereignty, understood as a power limited only by law, posited or accepted by that same will.
Catholic doctrine cannot accept these theoretical positions, but, starting from the principle that force, being in itself a means neither good nor bad intrinsically, cannot receive the seal of moral and juridical legitimacy unless it is directed to the attainment of an end that is just in its essence, also with regard to hostilities in time of peace, reaffirms its position, declaring them lawful if they are placed at the service of law, for its defense or its reparation, and in the contrary case unlawful. It does not, therefore, exclude the faculty of the State to have recourse to the use of violent means; it only subordinates it to the higher norms of natural justice and restricts its exercise within their sphere, denying the double axiom of voluntarism and of unlimited sovereignty. Acts of hostility which do not interrupt ordinary relations by the mere fact of their being taken are considered to be: retorsion, sequestration, embargo, reprisals, and pacific blockade.
Retorsion consists in opposing to an act contrary to law, to interests and to equity an act which may be of the same kind, in order to compel a State to acknowledge its own wrong and to withdraw from the measures taken. By sequestration a State takes possession of a good belonging to another in order to extort reparation for a wrong suffered. Embargo is a special sequestration, which has as its object the merchant ships of the opposing State, from which therefore warships are excluded. With regard to reprisals, v. the corresponding entry. Blockade, finally, occurs when the ports or the strongholds of the adversary are closed to all commerce, and it can therefore be maritime or continental. It is superfluous to note how 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 procedure can derive, but also the well-being of the international community and the possible complications harmful to it, to which, according to the principle already established by Vitoria with regard to war, even the defense of a certain right remains subordinate. In the case, moreover, of retorsion and reprisals, every act contrary to the laws of humanity and to the most fundamental rights of the human person must be deemed unlawful, even if taken by another State.
II. HOSTILITY BELLICHE
1. Beginning of hostilities
For a long time the practice prevailed of not beginning hostilities without having first made known to the adversary, in any manner whatsoever, the will to refer the settlement of the pending question to the judgment of arms. For this purpose heralds were usually sent, who, by letters of defiance or verbally, made known the will of their sovereigns and the reasons for which these judged it necessary to resort to violent means. Subsequently this custom was lost; States, moved both by new amoral conceptions of war and by falsely alleged military exigencies, which would have suggested a rapid beginning of hostilities, in order to catch the enemy by surprise, began to dispense with every formality, proceeding to the attack without any prior declaration. The new practice, having replaced the older one, must be regarded as a progressive departure from the natural norms of just war. War, in fact, is legitimate only against a State guilty of a grave violation of another's right, which it has obstinately refused to repair peacefully. It therefore takes on the character of ultima ratio or of an extreme means, morally and juridically employable, only in the case that the ordinary means of settlement have been tried in vain. It is therefore necessary that, before proceeding with force against one who has violated the right, he be granted time to repair, if he wishes, the wrong committed. The original incident must form the object of prior negotiation, of conciliatory proposals and of compromise, and be submitted, if possible, to an arbitral process, in order to achieve a consensual agreement. If then all efforts to resolve the conflict peacefully fail, the beginning of hostilities must always be preceded by a solemn warning, which places the obstinate State before its own responsibilities and makes it aware that the hour of negotiations has already passed. In order not to destroy the last probability of a peaceful solution, which still subsists at the moment of the declaration of war, a reasonable interval should be fixed between it and the actual beginning of hostilities.
This principle, derived from a moral conception of war, was adopted by the Hague Conference of 1907, which in art. 1 of Convention III provided that hostilities must not be begun by the contracting powers without a prior and unequivocal notice, having either the form of a motivated declaration of war, or that of an ultimatum with a conditional declaration of war. The same convention, however, does not require, nor determine, that an interval must elapse between the notification and the beginning of hostilities, the attempts of some delegations to have a minimum term of 24 hours fixed having failed. The derogations from the norm recalled have become, particularly after its acceptance, so numerous as to suggest that States do not feel themselves bound by it, as they should, opposing to it a contrary custom, condemnable for higher reasons of morality and justice. The carrying out of hostile acts, an expression of the will to establish the state of war, even if not preceded by any intimation or declaration, in every case puts an end to peaceful relations, suspending the ordinary law that governs 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 dominated throughout the course of the war.
2. Conduct of hostilities
Not a few political theories, or apparently juridical ones, exist at the present time which maintain the full freedom of States in the use of means of offense against the adversary, in order to break his resistance rapidly. It has been asserted that war, essentially inhuman, cannot be humanized, and even that the most humane war would be that which with implacable methods shortens the time of the struggle, breaking the enemy's force more rapidly. It has been added from the juridical aspect that, war being a complex of hostile acts outside the law and against the law in force among States, it cannot for itself be subject to law, and falls therefore within that sphere of unregulated freedom, where everything is permitted. A relationship of force, and which from force awaits to be regulated, can have as its criterion none other than this force itself, which must be left free to exercise its own pressure on the adversary with all the means at its disposal.
The theses just outlined, which are connected to conceptual positions (for which v. GUERRA), have as their common foundation the amoralism of armed struggle and the cult of force, as the generator of law, and cannot be accepted by Catholic doctrine, which energetically rejects them. War is not an unleashing of cosmic forces or of the biological instincts of the species, as some have wished to define it, but is a struggle between men and therefore involves a series of human acts, which, by the same standard as all other human acts, are subject to the laws of morality, justice and humanity. Moreover, war is in itself a use of force, which derives its justification from an end, the defense and reparation of the right threatened or violated, and therefore from the same end derive the limits within which hostilities must be contained. This finalistic principle, implicitly enunciated by Vitoria when he affirms that in a just war there is the right to do whatever is necessary for the defense of the public good, has been constantly applied to the conduct of hostilities by the subsequent Catholic tradition, by Suárez, by Molina and by other later authors.
Associated with it has been the distinction, with regard to the faculty of offense, between nocentes and innocentes, that is, between combatants and non-combatants, with the moral and juridical rule of sparing the latter from direct offense. Thus a principle of humanity was made to prevail over the use of force, first in a practical manner imposed by ecclesiastical authorities in the "Peace of God," and then theorized as a source of moral obligation. The bases, therefore, on which Catholic thought founded the doctrine on the conduct of hostilities are: the distinction between licit and illicit means of offense, deduced from the finalistic criterion of war; and that between combatants and non-combatants, drawn from the same principle and from the laws of humanity; to these, in a subordinate manner, was added that of loyalty, already hinted at by St. Thomas (Sum. Theol., 2ᵃ-2ᵃᵉ, q. 40, a. 3), who excluded the licitness in time of war of deceiving the enemy, affirming the false and not observing promises, since there exist "quedam iura bellorum, et foedera etiam inter ipsos hostes servanda."
The practical consequences of these principles regarding what is licit or illicit in the conduct of hostilities are easy and evident. Systematically they have been deduced better than by any other by Taparelli. The purpose of war, he says, consists in reducing to order by force; consequently everything that cannot offer resistance must not be destroyed. Here, then, is condemned all vandalism, the useless destruction of houses and goods, the indiscriminate slaughter of the old, women, and children. Every evil not necessary to break the enemy's force is forbidden in humane war by the very end of war. The same law of avoiding an unnecessary evil forbids among nations the use of certain means of offense, whose effects art could not control, directing their damage against the forces of resistance. To spread contagion, to poison waters and other similar chemical or bacteriological means, must be understood as forbidden. The same Taparelli adds further: if it is forbidden to do an unnecessary evil, with greater reason it is forbidden to do moral evil. Treachery, perjury, the parricidio or sacrilege must not occur in war between men, and the sanctity of truces and armistices, respect for the dead, humane treatment of the wounded, discretion in the requisitioning of provisions, and so on, must be observed. The uncertainties regarding certain methods of warfare, still admitted as lawful by medieval and 16th-century authors under the pressure of the crude customs then in force, came to an end in the more mature elaboration of Taparelli, which has by now become common doctrine in Catholic thought.
3. Positive law and hostilities
Positive international law has accepted the principles set forth and their practical consequences. In various conventions States have gradually expanded the code of the laws of war, so as to mitigate appreciably, at least in the texts of the agreements, the harshness of hostilities. In this connection, the following should be recalled here in chronological order: the Geneva Convention of 1864 for the improvement of the condition of wounded soldiers; the St. Petersburg Declaration of 1868 to exclude the use of exploding bullets; the various Hague Conventions of 1899, 1904 and 1907 concerning the laws and customs of land and maritime warfare; 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 poisonous gases and of bacteriological means; and finally the Geneva Convention of 1929 for the improvement of the lot of the wounded, the sick and prisoners.
The outline just traced 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, to grasp this progress it will suffice to note its general lines. The principle enunciated by art. 23 of the Hague Regulations of 1907, according to which belligerents do not have an unlimited right in the choice of means of offense, must be regarded as a norm accepted by the majority of States. Their right is circumscribed both by the aims at which war is directed, from which means that are uselessly cruel are excluded, and by the laws of humanity. This criterion, which was explicitly mentioned in the preamble of the St. Petersburg Convention of 1868, informs all the positive provisions on the conduct of hostilities. Moreover, the distinction between combatants and non-combatants, with the consequent prohibition of directly harming the latter, must still be regarded as a norm of present-day 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 those procedures that can deceive the enemy and cannot be reduced to military stratagem.
With regard to means of offense, the Regulations annexed to the Convention just recalled prohibit the use of poison and of poisoned weapons. This provision must be supplemented by the second Hague Declaration of 1899, which prohibits bullets that release asphyxiating and deleterious gases, a prohibition reaffirmed by the Washington Convention of 1922. There follows the prohibition of killing or having killed by treachery individuals belonging to the enemy State, of killing or wounding the enemy no longer capable of defending himself or who has surrendered at discretion, of employing weapons and projectiles capable of causing superfluous injury. Particular provisions regulate the treatment of the wounded, the sick and prisoners of war, the latter of whom may not be put to death.
The use of stratagems is not prohibited; nevertheless the Hague Regulations of 1907 expressly prohibit the unlawful use of the white flag, of the flags and uniforms of the enemy and of the distinctive signs of the Red Cross, and all those procedures that constitute acts of perfidy or are contrary to military honor. Also prohibited is the giving of no quarter, admitted by certain particular legislations in case of necessity, a convenient means of evading the mandatory prescriptions of law. Necessity can never legitimize the violation of the norms of justice and humanity.
4. The Church and the conduct of hostilities
The provisions of positive international law summarily described derive from the Christian tradition, which labored, through the ecclesiastical hierarchy, to soften the customs of war.
The movement in favor of a greater sense of humanity in the conduct of hostilities began in the Middle Ages in France, where several local and regional councils issued prescriptions in this regard. The Council of Narbonne of 990, for example, imposed excommunication against those who had struck the cenobites of Cluny and took other measures to restrain hostilities (Hefele-Leclercq, IV, pp. 869-70 and 869 note 2). In 989 the provisions in favor of combatants had already been extended, with the Council of Charroux near Poitiers, from ecclesiastics and the goods of the Church to peasants and the poor, striking with excommunication anyone who had deprived them of their goods, to travelers and merchants (loc. cit.). Under the auspices of the Church, around 997 a league was created for the maintenance of peace, in which laymen took part with deliberative functions, with the obligation to assist the bishop in repressing acts of violence committed within his territory (loc. cit.), later transformed, in 1908, into a compulsory peace association, in which all men from the age of fifteen had to enroll and take an oath. The Holy See did not fail to promote the "peace of God"; as early as 1930, the legates of Pope John XIX went from council to council, to impose it and to strike the transgressors with anathema (ibid., p. 960 ff.).
The "truces of God" contributed to softening the customs of war. The Council of Elne of 1027 (ibid., p. 969 f.), after confirming the protective provisions for clerics, monks and women, determined that after the ninth hour of Saturday until the first hours of Monday it was forbidden to all to attack their enemy. The truce of God, at first a simple application of the precept of festive rest, was extended also to other days and to particular liturgical seasons, such as Advent and Lent. A legate of Pope Alexander II, in 1068, introduced it into Spain; two councils, that of Melfi of 1089 and that of Troia of 1099, into Italy (ibid., V, pp. 345 ff., 371 ff.). In 1095, Urban II, present at the Council of Clermont, wished to extend to the whole Church the institutions of peace in view of the Crusade. The peace of God and the truce of God would be confirmed by Paschal II (1107) and by Callistus (1119, ibid., V, p. 581 ff.).
With regard to the use of means of offense, Innocent II at the Lateran Council of 1139 prohibited the employment of ballistae and arrows. In 1179 Alexander III renewed the prescription that priests, clerics, monks, conversi, pilgrims, merchants, peasants traveling or engaged in agriculture and their animals should enjoy appropriate security. These prohibitions and prescriptions were renewed by Innocent III (ibid., V, pp. 728-29, 1103). The Church further influenced the customs of war in a beneficial sense with the institution of chivalry and with the Third Orders.
It is today a common opinion among historians of international law that particularly the laws on the conduct of hostilities derive from the constant effort of the Church, which knew how to make penetrate into the still savage soul of peoples certain principles of humanity, which, later developed theoretically by the first Catholic systematizers of international law, have become the heritage of civilized nations, as part of modern positive law.