What The Catholic Church Teaches About War and Peace

According to Catholic social teaching, the purpose of political society is to promote peace. By peace is meant the “tranquility of order,” as St. Augustine called it—that is, the serenity that results from people living in proper relation to one another, acting justly toward one other, and helping the community to thrive.  

We call the order of people properly relating to one another social justice and the peace that results civil peace, or peace within a community. Peace between and among nations we call international peace. 

According to the Catechism, the Fifth Commandment, “You shall not kill,” obliges all citizens and all governments to work to avoid war (CCC 2308). War involves destructive conflict, inevitably including some unjustifiable killing; however, the Catholic Church teaches that war can, under limited circumstances, be justifiable. According to Vatican II, nations may lawfully defend themselves if all reasonable efforts at peace have failed (Gaudium et Spes 79; CCC 2308). The principles for the justified use of military force are included in what is traditionally known as the just-war doctrine. These principles (CCC 2309) are essentially defensive: 

1. The damage inflicted by the aggressor on the nation or community of nations must be lasting, grave, and certain.
2. All other means of ending the aggression must be known to be impractical or ineffective.
3. The prospects of success of the military action must be serious.
4. The armed response must not create greater evils than the evil to be prevented by military action.
5. It falls to the prudent judgment of those with authority for the common good to determine whether military action is morally justified. 

The Church also insists on applying moral principles to conduct of the war: “The mere fact that war has regrettably broken out does not mean that everything becomes licit between the warring parties” (Gaudium et Spes 79; CCC 2312). The moral principles governing a just conduct of war (CCC 2313-14) include: 

1. treating noncombatants, wounded soldiers, and prisoners respectfully and humanely;
2. not obeying morally illegitimate orders such as commands to commit genocide. “I was just following orders” doesn’t justify committing atrocities; and
3. not committing indiscriminate attacks and destruction. Civilians and noncombatants may not be intentionally attacked nor may otherwise justified attacks on military targets disproportionately harm noncombatants as a foreseen yet unintended consequence. (For example, it wouldn’t be morally acceptable to annihilate the whole population of a city to ensure the destruction of a nearby bomb factory.) 

Related to the issue of war is the question of the development of weapons of war. Obviously, if a nation has a right to defend itself and to safeguard its people, it also has the right to obtain the means necessary to do so. At the same time, a disproportionate effort to secure arms can contribute to an atmosphere that makes war more likely. It can also redirect a nation’s resources away from its citizens’ urgent needs (CCC 2316). 

Jesus teaches, “Blessed are the peacemakers, for they shall be called sons of God” (Matt. 5:9). Catholic social teaching encourages the Lord’s disciples to be peacemakers. Nations can foster peace in many ways, including by working to reduce the conditions threatening peace, such as envy, distrust, unjust social inequalities, and pride among peoples (CCC 2317).

With wars raging around the world, what does the Church teach about war and peace? Get answers in the new Big Book of Catholic Answers, Volume 3. Order today!