Question Three: Concerning the Defense of the Common Good or On War

S. Th. II-II, q. 40.

272. War is a means of defending the common good of the political community against foreign enemies: namely, the public taking up of arms for the sake of protecting or vindicating the commonwealth. It can be defined: a conflict by force and arms between two or more nations; or the fight of a multitude or commonwealth with a foreign multitude or commonwealth, undertaken by public authority for the common good.

It differs: a) from a brawl, which is undertaken in a private capacity and is of one or a few against one or a few, and not always with arms;

b) from a duel, which is a contest with arms, but singular, not of a multitude, and is instituted by agreement;

c) from sedition, which is an uprising or conflict of a multitude against the prince, or against the political society to which it belongs, or the fight of a multitude against a multitude in the same community; whence it is, as it were, civil war.

Hence St. Thomas, q. 42, a. 1: "War properly is against foreign enemies, as of a multitude against a multitude; but a brawl is of one against one, or of few against few; sedition, however, is properly among the parts of one multitude disagreeing among themselves, for instance, when one part of the political community is stirred up in tumult against another."

War is either offensive, when it is undertaken to avenge or obtain reparation for an injury inflicted by another nation; or defensive, when it is sustained for repelling unjust force by force, namely, an aggression made by another prince or kingdom, or for warding off an injury which is being inflicted here and now.

Ordinarily offensive war is waged by him who first begins hostilities; not always, however, because sometimes an apparent aggression is nothing other than necessary defense.

273. Principle I. War can be undertaken justly; for this a threefold condition is required: the authority of the supreme civil power, a just cause, and right intention.¹

¹ On war, besides St. Thomas in the cited place with the commentary of Cajetan and Bannez, one may consult Fr. de Victoria, Relectiones morales, l. IV, de iure belli; — Suarez, De Charitate, on II-II, q. 40; — Grotius, De Iure belli ac pacis; — Pufendorf, De Iure naturae et gentium; — Van der Pol, Le Droit de guerre d'après les théologiens et les canonistes du moyen âge, 1911; La Guerre devant le christianisme, 1912; La Doctrine scolastique du droit de guerre, 1919; — Michel, Questions théologiques du temps présent: I. Questions de guerre, 1918; — Strattman, Weltkirche und Weltfriede, 1925 (Dutch translation); — La société internationale, edited by 4 professors of Lille, 1928: I. La doctrine by Fr. Delos, ch. 5: war; — Bulletin catholique international, in which periodical several things deserve to be read, as for example Flajolles: Que disent nos manuels sur le droit de guerre, 1930; — Delattre, La religion et la paix; — Conclusio conventus theologici Friburgensis de Bello 1932, in Docum. de Vie intell. t. X; — Deux façons d'envisager la paix, in Vie intell. t. XIV, 1932; Regout, La doctrine de la guerre juste, 1935. — Also Benedict XV, in the peace proposals of August 1, 1917.

A. The first part is proved: War is sometimes just and licit, if for some people it is the only means for vindicating its own rights of great moment, or for defending its own existence.

Hence a) God also at times commanded war, and Scripture sometimes approved it. Cf. Gen. XIV; Ex. XVII; Deut. VII, XXIII; Num. XXI, XXV; Jos. I, VI, VIII, X; I Reg. XV; II Reg. VIII; Hebr. XI, 29 sq.;

b) so holds the common doctrine of the Fathers and theologians, against the Manicheans and Quakers condemning every war as illicit, against the Wycliffites and Erasmus forbidding it to Christians, and against Luther prohibiting war against the Turks, since God visits our iniquities through them. Cf. Ambrose, de Off., l. I, c. 40; Augustine, c. Faust., l. 22, c. 74; Gregory, l. I, epist., 72;

c) the Church herself decreed war for recovering the Holy Land.

B. The second part is proved. Three conditions are required:

1. The authority of the supreme civil power, both because a private person, or a non-supreme authority, can pursue right in the judgment of a superior judge, and therefore does not need war in its own cause, and because it does not belong principally to such an authority to procure the common good or to call together the multitude, which must be done in wars.

"But since," says St. Thomas, a. 1, "the care of the republic has been entrusted to princes, it pertains to them to protect the republic of the city, or kingdom, or province subject to them. And just as they licitly defend it by the material sword against interior disturbances, when they punish evildoers,... so also it pertains to them by the warlike sword to protect the republic from exterior enemies." Because, Billuart notes,² "by this very fact, that among princes who have no superior one offends another, the offender becomes subject to the offended, in this sense, that the offended can punish the offender according to the measure of the injury." — Authority sometimes resides in the prince alone, sometimes in the prince together with the consent of the legislative assembly.

² De Charitate, diss. 7, a. 3.

2. A just, proportionate, grave, and necessary cause, which can be remedied by no peaceful means, or the necessity of the common good: "To wage war is not a matter of will, but of necessity." But since war is apt to cause immense damages, especially in our times, and to be harmful to both sides, a most grave cause is required: namely, an injury received whose reparation or repulsion cannot be had in another way, and which is so grave that it outweighs the immense evils which war brings. For to save a good of a higher order, or to avoid a greater evil, even the community itself must yield its strict right.

For defensive war, however, the conditions of just defense suffice, which is to be undertaken with the moderation of blameless protection.³ But for offensive war, "the one and only just cause of inflicting war is an injury received,"⁴ a grave injury inflicted and not repaired nor to be repaired in another way.

³ Cf. below, n. 361.

⁴ Fr. de Victoria, Relectiones, de iure belli, n. 13.

In particular the cause can be: the unjust invasion or detention of a province or city by enemies; grave injuries inflicted either upon the nation itself, or upon ambassadors, or upon citizens, which a foreign nation obstinately refuses to repair; the recovery of a grave debt, the protection of rights of great moment, or of things necessary for existence; the unjust violation, as they say, of neutrality or of a treaty, or help given to an unjust enemy; the necessity of bringing aid to an ally or another people unjustly oppressed, whence proposition 62 of the Syllabus is condemned: "The principle which they call non-intervention is to be proclaimed and observed"; religion or the right of preaching the Gospel, to be protected from aggressors against unbelievers, as St. Thomas teaches, q. 10, a. 8: "the faithful of Christ frequently move war against unbelievers, not indeed in order to compel them to believe,... but for this, that they compel them not to impede the faith of Christ." — But these do not suffice: diversity of religion or the desire of converting unbelievers to the true faith; the enlargement of one's own empire; singular progress or a superior culture of a nation which surpasses others; the power of a prince or neighboring nation to be diminished lest it be able to harm (it is illicit to kill men lest they be able to harm); one's own glory; a claim of expediency; celebrity of name; or the private good of the prince or of his family; the benefit of imparting a higher civilization even to the uncultivated or barbarians. If, however, a people altogether needs a more ample territory, as if it has more citizens than it can nourish, and there are regions little cultivated because of the paucity, ignorance, or laziness of the inhabitants, it does not seem unjust by peaceful means to occupy territories nearly empty, with equitable compensation given to the natives, because the earth is destined for the subsistence of all from primary natural right; and this right, even by moderate force, if it should be necessary, it is licit to protect.

But the cause must be a) deliberated, or subjected to mature and prudent examination, with upright men and experts in international law also consulted; b) morally certain, both because otherwise a doubt of fact would expose one to the danger of inflicting unjust damage, and because no one can be despoiled or punished unless the injustice or delict is certainly established (n. 91); c) necessary, so that other ways of satisfaction are first attempted, by which the dispute may be settled peacefully: by sending ambassadors, by recurring to mediators or arbiters, as often as this can be done without dishonor; but if the offender offers full satisfaction, the offended is bound from justice to accept it: for when the just cause ceases, the war becomes unjust.

3. Right intention of justice and of the common good, "by which, namely, it is intended either that good be promoted, or that evil be avoided." Therefore war is not to be waged from hatred, vain glory, private vengeance, desire of harming, cruelty of avenging, lust of dominating, or an implacable spirit, but from love of the common good.

Therefore the end of war is peace, or the tranquillity of order. Hence St. Thomas, a. 1, ad 3: "Even those who wage wars justly intend peace; and thus they are not contrary to peace, except an evil peace, which the Lord did not come to send upon the earth, as is said in Mt. X, 34. Whence Augustine says to Boniface (ep. 205): Peace is not sought in order that war may be exercised; but war is waged in order that peace may be acquired. Therefore be peaceful in warring, so that by conquering you may lead those whom you attack to the utility of peace."

274. Principle II. For waging war justly and licitly, even a just war, both the natural law and the prevailing statutes of the law of nations and international agreements must be observed. — For evils must not be done that goods may come. Hence a) in a just war all things are licit which are necessary or apt for obtaining the end and are permitted by right: for he who has a right to the end has a right to the means. On the contrary b) those things which are forbidden or useless cannot be employed without injustice, and therefore damage thus inflicted must be repaired. — But by present-day right:

A. The principle holds: War is not waged against private citizens, but against the nation as a public person.

Hence 1) it is licit to besiege fortified strongholds and deprive them of water or food so that they surrender more quickly; to fire artillery against them even with the danger of indirectly killing the innocent; to destroy private houses, monasteries, churches when enemies use them for defending themselves; to destroy the walls of a city, etc., insofar as these things are necessary or useful for conquering the enemies and done with the permission of the commander; — but not to infect springs or wells with poison, or to use poisoned weapons, because these things are cruel and not necessary: namely, the manner of waging war must be humane, withdrawing from all savagery and ferocity;

2. it is licit to render harmless by armed force those fighting and existing under arms, and for this to wound them, indeed, if it is necessary, directly to kill them; not however enemies already captured (unless by sentence of a judge they were proved guilty of a more grave crime); — a fortiori it is illicit directly to kill or reduce to captivity ambassadors, or hostages (even if they consented to death, because they are not masters of their own life), or innocents, such as children, women, old men, clerics, religious, merchants, etc., who are presumed to be not armed and contributing nothing to the war, or pilgrims or foreigners;

3. it is licit, on account of the expenses of war, to impose upon captured cities or regions taxes proportionate to the resources of the inhabitants, and to require from them things necessary for sustaining the army; — not however, by received right, to hand over a captured city to the army as prey, or in land war to usurp the goods of private persons without necessity or equitable compensation; the contrary holds in naval war; a fortiori it is altogether illicit to despoil or take the goods of guests, foreigners, or the Church;

4. it is licit to set ambushes for enemies and to use stratagems to overcome them, for example, simulated flight, feigned aggression, deceptive signs, the obtaining of intelligence, etc.; — but betrayals, violations of treaties or even of a true promise, or frauds which can be guarded against by no prudence, are not licit, such as infecting springs with poison, suborning assassins who secretly slaughter, etc.;

5. reprisals are dangerous and easily provide occasion for more grave evils; — nevertheless they can be licit, but exclusively by command of the prince, where the injustice inflicted is established, satisfaction cannot be had otherwise, and they are exercised against guilty persons or against goods, and just compensation is not exceeded.

B. War is not to be begun before a formal declaration of war is made, which ought to be preceded by an ultimate warning, that is, an intimation concerning war about to be undertaken immediately unless such and such a due condition is fulfilled.

Thus a final opportunity is given to the enemy of repairing the injury inflicted, and, to foreigners staying within the borders of the territory, time within which they can provide for themselves and their goods.

C. When the enemy has been conquered and asks for peace, equitable and moderate conditions are to be established, without harshness or a spirit of harming. For, as Fr. de Victoria notes,⁵ the victor ought to pronounce concerning the conditions of peace, not indeed as victor or as accuser or enemy, but as an equitable judge and according to the rights and merits of the cause; and to dictate those conditions by which international order may be restored, namely the order of justice and cooperation, so that good relations between the victor and the conquered may again be possible. Therefore it is unjust to impose harsh or excessively burdensome conditions, or to bring on the ruin or destruction of the adverse nation.

⁵ Cited work, at the end.

Nevertheless these can be demanded in a just war: just satisfaction of the right on account of which the war was declared; — indemnities for necessary expenses of war and damages, but proportioned to the means and resources of the conquered; — also moderate precautions for security, if it is necessary.

Treaties of peace, since they have been entered upon for the common good of nations, must be altogether observed, unless they are certainly proved to labor under most manifest injustice; and this is not easy.

275. Corollaries.* — 1. He who declares war without a just cause sins gravely: first and formally against charity, because he disturbs peace, which is an effect of charity; at the same time, however, against justice, on account of the unjust damages which war is apt to inflict.

2. War per se and from its nature cannot be just on both sides, namely, materially or objectively, because right cannot belong except to one or the other, since contrary rights do not exist concerning the same thing; nevertheless it can be just on both sides subjectively and formally, but per accidens from invincible ignorance or good faith.

3. In doubt concerning the justice of the cause, recourse must be had to an amicable composition or transaction, or to the arbitration of others, especially of the Supreme Pontiff, or to an international tribunal of peace or a society of nations; — but if the other party rejects recourse or refuses to obey the sentence given by the arbiter, there is now a certain injury on account of which, if the cause is proportionate, it is licit to wage war.

4. In a just war, commanders and soldiers called by precept or legitimately hired are bound to serve the community to be defended, even with danger of life: for the common good demands this. Hence they cannot desert; and per se deserters are bound to return to camp; but those who would flee to the enemy to help them would be traitors guilty of a most grave crime.

5. Soldiers — not so the learned and theologians — ordinarily are not able to judge concerning the justice of a war, nor are they bound as far as possible to inquire concerning it, unless the contrary would seem very probable, but they can presume it to be just. Even in positive doubt concerning the justice of the war, subjects who have been ordered or previously enrolled can and are bound to serve as soldiers, because presumption stands for the superior commanding; — non-subjects, or those not ordered or not hired, but free soldiers who of their own accord wish to fight, cannot enlist unless morally certain of the justice of the war, lest, namely, they involve themselves in the danger of inflicting grave injuries.

6. In a war plainly unjust, no one, neither subjects nor foreigners, can fight; because they would be cooperators in injustice. Hence they ought to withdraw from the war; but if they cannot do so without grave danger, they can exercise only actions indifferent of themselves, but they ought to abstain from fighting and hostile acts, and to surrender themselves to an enemy soldier whom they cannot avoid by flight; but if the enemy does not consent to this and nevertheless attacks, he himself now seems to become an unjust aggressor against an innocent man, and consequently the latter then probably can defend his life.

7. Today, on account of their greater security and the common good, it is strictly prohibited that merely private men, during war, involve themselves in military affairs or snatch up arms; and transgressors of this statute expose themselves to most grave penalties, even of death, which is not inflicted unjustly.

276. Observations. — 1. Today, because a society of nations has been instituted among several peoples, and because of the international pact which places war outside the law, cases are now rarer in which war occurs or offensive war is licit and just. Nevertheless it is not impossible, because nations, just as they freely enter the society of nations, so also can freely leave it, nor must all conflicts be subjected to it; moreover, the international pact has not been concluded or ratified by all peoples; and it could also happen that some nation would not wish to submit itself to an arbitral sentence.

Nevertheless, because of these new circumstances, a) it will now be easier to judge concerning the justice or injustice of a war, and, when war has been declared, cases of licit or obligatory flight or abstention will be more frequent; — b) subjects can now more easily demand from rulers that a conflict be submitted to arbiters; — c) or also that military expenses and the number of soldiers be notably diminished, since these have been increased and multiplied beyond every proportion of necessities.⁶

⁶ Benedict XV said, in the peace proposals directed to the belligerent princes on August 1, 1917: "First of all, the fundamental point must be that the moral force of right be substituted for the material force of arms; whence a just agreement of all for the simultaneous and reciprocal diminution of armaments, according to rules and guarantees to be established, in the measure necessary and sufficient for maintaining public order in each State; then, in substitution for armies, the institution of arbitration, with its high pacifying function, according to norms to be agreed upon and sanctions to be determined against the State which would refuse either to submit international questions to arbitration or to accept its decisions."

2. To serve as soldiers, which by natural and divine right is less fitting for clerics and religious, is strictly forbidden by ecclesiastical law (can. 141), unless by urgent necessity, or unless it has been dispensed by the Church (a. 2). They can, however, take part in war so that they may be present to those fighting with spiritual or bodily help (ad 2); indeed, they can exhort them to fight for the fatherland in a war that is not certainly unjust (ad 3): nevertheless, in judging concerning this matter, let them be prudent.

3. On feast days, just as from judicial business, so also from war one must abstain, especially because of the public unrest which draws back from divine worship; unless, however, necessity is present (a. 4).

4. Princes and commanders by office ought to take care of military discipline and restrain plunder, thefts, arson, and rapes, etc.; otherwise they are bound to restitution in solidum together with the soldiers; but the latter individually, unless they inflicted injustices from a true conspiracy. See below, n. 316-317.