Catechism of the Catholic Church

Life in Christ 559 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. 2329 “The arms race is one of the greatest curses on the human race and the harm it inflicts on the poor is more than can be endured” ( GS 81 § 3). 2330 “Blessed are the peacemakers, for they shall be called sons of God” ( Mt 5:9).