Just War Tradition
For, although we are in the flesh, we do not battle according to the flesh.
~ 2 Corinthians 10:3
The Catholic Church’s teaching on war is clearly set out within the fifth commandment: “Thou shall not kill.” As Catholics, we are called to resist resorting to violence as a means to resolve conflict and to encourage others to explore other means of resolution. However, the Church does recognize that in some dire cases, entering into a war may be necessary in order to ensure the overall safety of the country.
The Catechism of the Catholic Church teaches that:
“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.” 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” (CCC, no. 2307 -2308).
The legitimate need for military defense is outlined by several specific criteria.
The damage inflicted by the aggressor on the nation or community 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 modern means of destruction weighs very heavily in evaluating this condition.
These are the traditional elements of what is considered the just war doctrine (CCC, no. 2309).
World Day of Peace (USCCB)