Question Seventh. On War

351. Declarations. a. War is a fight of multitude with an external multitude, undertaken on account of the common good by public authority.

b. War is distinguished as offensive, which is instituted either for avenging an injury or for recovering possession, and defensive, which is instituted for repelling by force the force brought by another republic.

War differs from a brawl, which is done in a private name and is of few or single persons against few or single persons; it differs from sedition, which is a fight of multitude against multitude in the same republic or city; it differs from a duel, which is a single combat, not of a multitude, and is instituted by agreement.

¹ Cathrein, Moralphilosophie^4, II, p. 611 ff.; Meyer, Institutiones iuris nat., II, n. 732 ss.; Kirchenlexikon^2, Krieg.

352. On the lawfulness of war. 1. War, both defensive and offensive, is licit if the due conditions concur. Defensive: for if it is licit for a private man to repel force by force, the same will also be licit for the republic. Offensive: for the law of nature gives to each one the power of prosecuting his right or avenging an injury inflicted by public authority; therefore the same power of prosecuting right or avenging an injury belongs also to a prince if his right has been injured by another prince. But since princes do not have a higher authority, they cannot prosecute their right or avenge an injury inflicted on them except through offensive war.¹

2. In a just war all things are licit which are necessary or apt for obtaining the end, provided they are permitted by the law of nature and by the law of nations. For he who has a right to the end also has a right to the necessary or useful means. Therefore those things which are neither necessary nor useful to the end of war, or which are interdicted by the law of nature or by the law of nations, cannot be inflicted on enemies without injustice, and therefore damage inflicted in this way must be repaired.

Therefore it is licit to prepare ambushes and to employ stratagems, for example, to feign flight; but it is not licit to employ frauds which can be guarded against by no prudence. - It is licit to besiege cities and deprive them of water, to discharge artillery against them, to destroy monasteries and churches if enemies use them to defend themselves; but it is not licit to infect wells or fountains with poison. - It is licit to kill all those fighting against one or existing in arms, of whatever condition, state, or sex, until perfect victory has been obtained; but it is not licit directly to kill the innocent, nor ambassadors, who by the law of nations are inviolable, nor is it licit to suborn assassins who may secretly kill the commander. The innocent, whom it is not licit directly to kill, are children, women, old men, pilgrims, rustics, merchants, etc., who are not found in arms. Captured enemies cannot be killed by today's law of war; for they can be killed insofar as soldiers fighting in an unjust war are guilty of a grave crime, on account of which the penalty of death may be inflicted on them. But in our times fighting soldiers, as compelled men, cannot be considered guilty of a grave crime. - Private goods of enemies by the strict right of war can be given to soldiers as spoil; for citizens of a hostile region are considered participants in the injustice on account of which war is brought. Yet by today's custom it is not licit to give the private goods of enemies as spoil unless a special reason exists, as if some private person or some village had exercised a special hostility.

3. After the owed thing has been recovered, or after the injury has been sufficiently avenged, the victor is bound to accept peace offered on just conditions: for when the just cause ceases, the war becomes unjust. Accidentally, even the conquered is sometimes bound to accept peace, lest he expose himself and his subjects to greater damages.

¹ Cf. St. Thomas, II-II, q. 40, a. 1.

353. Required conditions. The just conditions under which it is licit to bring war are three:

a. Supreme authority: for if a greater authority is present, this ought to settle the controversy and avenge the injury inflicted.

Yet if the supreme authority either did not wish or were unable to avenge the injury inflicted on a subordinate society, necessity itself seems also to give to the subordinate republic the right of bringing war upon enemies.¹

b. A just and grave cause. The sole just cause of offensive war is an inflicted injury which the enemy refuses to repair. Hence, that war can justly be begun, it is required that satisfaction be demanded from the opposing party; and if it is offered, it must be accepted from justice. A grave cause is one which would outweigh so many evils coming from war both to body and to soul.

Causes of this kind, on account of which it is licit to bring war, are these: a province usurped by an adversary to be recovered; a grave injury inflicted on the republic to be driven away; religion to be protected against aggressors, even against unbelieving peoples who impede the preaching of the faith by expelling or killing missionaries;² a people unjustly oppressed to be defended. For the proposition (62) of the Syllabus is condemned: "The principle which they call non-intervention is to be proclaimed and observed," etc. But just causes are not: enlargement of the kingdom, glory of name, the power of a neighboring prince to be diminished, etc.

c. A morally certain right, if the war is offensive, or at least probable, if the war is defensive. The reason for the first is that the damages coming from war are so many and so great that it is not licit to declare it unless the right to be vindicated is certain; besides, no one can be despoiled or punished unless the unjust possession or delict is certain. The reason for the second is that, for force brought to be justly repelled, it suffices that it be probable that the force is unjustly brought.

There are not lacking authors who say that it suffices that the right of the prince bringing war be probable (Sporer, Azor) or more probable (Suarez, Victoria, St. Alphonsus). Others reject both (Elbel, Holzmann, Laymann, Tamburini). Genicot joins himself to these; citing Waffelaert, he has these things worthy of note (I, n. 383): "If doubt remains about the right, recourse must be had to the arbitration of other princes and especially of the Roman Pontiff: but if the other party wholly rejects this recourse, or refuses to obey the sentence given by the arbiter, then there will already be a certain injury, on account of which it will be licit to declare war."

¹ Laymann, l. 2, tr. 3, c. 12, n. 4.

² St. Thomas, II-II, q. 10, a. 8.

354. On soldiers. a. In a certainly unjust war it is not licit to serve as a soldier, and in the conflict itself it is not licit for soldiers to kill enemies, not even for the sake of defense: for they themselves are unjust aggressors. Therefore, if they cannot flee, they ought to see to it that by their blows they strike no one except the air.

b. In doubt concerning the justice of the war, a soldier who is a subject or hired before the war is bound to obey, both because a subject ought to obey unless the sin is certain, and because he ought to presume that the war is just unless the contrary is established.

c. But a soldier who is not a subject, or who is hired after the war has been declared, cannot serve as a soldier unless he is certain of the justice of the war: for since the matter concerns a very grave damage to be inflicted on another, it is not licit to inflict it unless it is established that the war is just. Yet if the war is defensive, a probable judgment concerning the justice of the war also suffices.

d. It is not licit for soldiers fighting in a just war to take away anything from the goods of enemies, except those things which are necessary for sustenance, unless the commander of the war has permitted it. Wherefore those things which have been taken away against the commander's will must of themselves be restored, provided he is unwilling with respect to the taking itself, not only with respect to the violated military discipline.

Although a war cannot be just on both sides, nevertheless it can happen that the soldiers of each side wage war with a safe conscience. For on the one hand grave authors deny that the right of the prince bringing war must be certain; and on the other hand soldiers usually do not know the more hidden causes of the war declared. But the causes which are spread abroad among the common people can seem just to them. Nor are they bound to inquire into the more hidden causes of war unless there is grave suspicion of injustice and at the same time hope of knowing the truth.

Theologians of an earlier time, having made a distinction between just and unjust war, absolutely forbid the plundering of fellow soldiers, and in a just war also of enemies; but they permit the plundering of enemies in an unjust war. In our time, by force of the law of nations or of international conventions, the plundering of the slain is absolutely interdicted; their goods, which can be recognized, pertain to their heirs.