1380. War is not against the law of God. (a) Under the law of nature Melchisedech blessed Abraham returning from victory over the four kings (Gen., xiv. 18-20). (b) Under the written law, God many times ordered or approved of war, as can be seen from Exodus and following books in numerous places. (c) Under the New Law, John the Baptist acknowledged the lawfulness of the soldier’s profession (Luke, iii. 14), a centurion was praised by Christ (Matt, viii. 10), Acts, x. 2, speaks of the officer Cornelius as a religious man, and St. Paul lauds warriors of the Old Testament such as Gedeon, Barac, Samson, etc. (Heb, xi. 32-34). Our Lord Himself used physical force against evildoers (John, ii. 14 sqq.).
1381. Certain sayings of our Lord—for example, that those who take the sword shall perish by the sword (Matt, xxvi. 52), and that one should not resist evil (Matt, v. 39)—are not an endorsement of extreme pacifism, but are respectively a condemnation of those who without due authority have recourse to violence, and a counsel of perfection, when this serves better the honor of God or the good of the neighbor. Moreover, these words of Christ were addressed, not to states, which are responsible for the welfare of their members, but to individuals. The Quakers have done excellent service for the cause of world peace, but their teaching that all war is contrary to the law of Christ cannot be admitted. The spirit of the Gospel includes justice as well as love.
1382. War is not against the law of the Church. (a) The Church has never condemned war as such. She has always labored for the promotion of peace or for the lessening of the evils of wars that could not be prevented; but her official declarations and the writings of the Fathers and Doctors show that she recognized that recourse to arms by nations is not necessarily sinful. (b) The Church has put her approval on some wars as necessary and laudable. Thus, the Crusades, to which the salvation of Christian civilization is due, were promoted by the Church; military orders for the defense of the Holy Sepulchre were instituted by her, and she has raised to the honors of the altar soldiers like Sebastian, Maurice, and Martin of Tours.
1383. War is not against the law of nature. (a) As the law of nature allows even a private individual to use force to drive off an unjust aggressor, it cannot be unlawful for a nation to have recourse to defensive war when its rights are invaded. (b) As the law of nature allows the individual to seek satisfaction for injury and restitution for loss, it cannot be unlawful for a nation to make offensive war when another nation will not make reparation, unless compelled to it by force. If physical coercion were unlawful, a conscienceless nation would take advantage of this at the expense of other nations, and thus a premium would be set on iniquity.
1384. Like every other act, war is not morally good, unless its object, its purpose and its circumstances are in accord with right. War is not lawful, therefore, unless the three following conditions exist:
(a) Hostilities must be authorized by the public authority, for the care of the State against internal and external disturbances has been committed to the ruler (Rom., xii. 4; Ps. lxxxi. 4), and the individual or the subject state can have recourse for protection of its rights to the higher authority.
(b) There must be a just cause for war, that is, some fault on the side of the other nation; for, if a nation may not use force against its own subjects without sufficient reason, much less may it do so against those who are not its subjects.
(c) There must be a right intention, that is, the desire to obtain some good or to ward off some evil. Even if war is declared by the proper authority and there is a sufficient reason for it, those who take part in the war are guilty of sin if they have evil motives, such as the exercise of cruelty, revenge, pride, or avarice. To delight in war because one loves excitement or wishes to show one’s skill or get promotion, is not a right frame of mind.
1385. What public authority has the right to declare war? (a) Ordinarily, only the sovereign power—that is, the person or body in whom the chief authority is vested according to the constitution of the nation—can make war. War is an act of the nation, and hence only the authority that represents the nation can make war. Subordinate bodies in a confederation or union of states have the right to make war, if custom or law allows it.
(b) In extraordinary circumstances, an inferior power can authorize war, as when war is necessary and it is impossible to await a declaration from the sovereign power. Thus, if a province were suddenly invaded, it would be lawful for the head of the province to make war on the invaders at once. It seems, indeed, that the head of a province could justly authorize the invasion of a neighboring state, to protect such province against aggressions, if the central authority would do nothing; for such a war would be really defensive.