Eastern Catholic churches permit military service and affirm the moral legitimacy of just war, in continuity with the broader Catholic tradition articulated since St. Augustine. States may legitimately use force to defend the innocent, repel unjust aggression, and maintain peace, and Christians may participate in such defense as an act of service.

Eastern Christianity has its own tradition of warrior saints (such as St. George, St. Demetrius of Thessaloniki, and St. Boris and Gleb), who are venerated in part for their military vocation and their combination of martial duty with Christian virtue. While peace and reconciliation are core Christian values, Eastern Catholic theology does not require pacifism and recognizes the moral legitimacy of military service when undertaken within the constraints of just war doctrine.