Today’s Catechism sections discuss war. Supporting material comes from the Pastoral Constitution, “Gaudium et Spes”.

Avoiding war

2307 The fifth commandment forbids the intentional destruction of human life. Because of the evils and injustices that accompany all war, the Church insistently urges everyone to prayer and to action so that the divine Goodness may free us from the ancient bondage of war.104

2308 All citizens and all governments are obliged to work for the avoidance of war.
However, "as long as the danger of war persists and there is no international authority with the necessary competence and power, governments cannot be denied the right of lawful self-defense, once all peace efforts have failed."105

2309 The strict conditions for legitimate defense by military force require rigorous consideration. The gravity of such a decision makes it subject to rigorous conditions of moral legitimacy. At one and the same time:
- the damage inflicted by the aggressor on the nation or community of nations must be lasting, grave, and certain;
- all other means of putting an end to it must have been shown to be impractical or ineffective;
- there must be serious prospects of success;
- the use of arms must not produce evils and disorders graver than the evil to be eliminated. The power of modem means of destruction weighs very heavily in evaluating this condition.

These are the traditional elements enumerated in what is called the "just war" doctrine.
The evaluation of these conditions for moral legitimacy belongs to the prudential judgment of those who have responsibility for the common good.

2310 Public authorities, in this case, have the right and duty to impose on citizens the obligations necessary for national defense.
Those who are sworn to serve their country in the armed forces are servants of the security and freedom of nations. If they carry out their duty honorably, they truly contribute to the common good of the nation and the maintenance of peace.106

2311 Public authorities should make equitable provision for those who for reasons of conscience refuse to bear arms; these are nonetheless obliged to serve the human community in some other way.107

2312 The Church and human reason both assert the permanent validity of the moral law during armed conflict. "The mere fact that war has regrettably broken out does not mean that everything becomes licit between the warring parties."108

2313 Non-combatants, wounded soldiers, and prisoners must be respected and treated humanely.
Actions deliberately contrary to the law of nations and to its universal principles are crimes, as are the orders that command such actions. Blind obedience does not suffice to excuse those who carry them out. Thus the extermination of a people, nation, or ethnic minority must be condemned as a mortal sin. One is morally bound to resist orders that command genocide.
IN BRIEF

2327 Because of the evils and injustices that all war brings with it, we must do everything reasonably possible to avoid it. The Church prays: "From famine, pestilence, and war, O Lord, deliver us."

2328 The Church and human reason assert the permanent validity of the moral law during armed conflicts. Practices deliberately contrary to the law of nations and to its universal principles are crimes.

The Pastoral Constitution, “Gaudium et Spes” (79) discusses war and its avoidance.

On the subject of war, quite a large number of nations have subscribed to international agreements aimed at making military activity and its consequences less inhuman. Their stipulations deal with such matters as the treatment of wounded soldiers and prisoners. Agreements of this sort must be honored. Indeed they should be improved upon so that the frightfulness of war can be better and more workably held in check. All men, especially government officials and experts in these matters, are bound to do everything they can to effect these improvements. Moreover, it seems right that laws make humane provisions for the case of those who for reasons of conscience refuse to bear arms, provided however, that they agree to serve the human community in some other way.

Certainly, war has not been rooted out of human affairs. As long as the danger of war remains and there is no competent and sufficiently powerful authority at the international level, governments cannot be denied the right to legitimate defense once every means of peaceful settlement has been exhausted. State authorities and others who share public responsibility have the duty to conduct such grave matters soberly and to protect the welfare of the people entrusted to their care. But it is one thing to undertake military action for the just defense of the people, and something else again to seek the subjugation of other nations. Nor, by the same token, does the mere fact that war has unhappily begun mean that all is fair between the warring parties.

Footnotes

104 Cf. GS 81 # 4.
105 GS 79 # 4.
106 Cf. GS 79 # 5.
107 Cf. GS 79 # 3.
108 GS 79 # 4.