What is the just war doctrine?

The just war doctrine is the Church's framework for judging when military force may be morally permissible and how it may be used. Its conditions are strict, and peace must always be actively pursued.

The starting point is peace. Jesus calls peacemakers blessed (Mt 5:9), and the Church requires governments and citizens to work for the avoidance of war (CCC 2307-2308). Christians may not be indifferent to aggression, genocide, or attacks on innocent people. Legitimate defense can be a grave duty for those responsible for protecting others, but war remains a tragic remedy after peaceful means have failed.

When force may be used. The Catechism lists four conditions that must all be satisfied before military force is justified:

1. The damage inflicted by the aggressor must be lasting, grave, and certain.
2. Every other practical means of ending the aggression must have proved ineffective.
3. There must be serious prospects of success.
4. The use of arms must not cause evils and disorders graver than the evil being resisted.

These conditions belong to the traditional principles of just cause, last resort, probability of success, and proportionality. The decision belongs to those who have legitimate responsibility for the common good, and their judgment is subject to moral law (CCC 2309). Private individuals or armed factions cannot simply declare their violence a just war.

Conduct during war also matters. A just cause does not permit every tactic. Noncombatants, wounded soldiers, and prisoners must be treated humanely. Deliberate attacks on civilians are gravely wrong, as are genocide and orders to exterminate a people or ethnic group (CCC 2312-2314). Military action must distinguish combatants from civilians and use no more force than necessary. Blind obedience does not excuse crimes against the moral law (CCC 2313).

What soldiers and citizens should remember. Those who serve honorably in the armed forces can contribute to the security and freedom of peoples (CCC 2310). The Church also recognizes conscientious objection when law provides for it, while expecting objectors to serve the human community in another way (CCC 2311). Decisions about a particular conflict often involve prudential judgment, but direct attacks on innocent people are never permissible.

Pray for peace, examine claims about war carefully, support civilians and refugees, and refuse rhetoric that treats any people as less than human.