Published in War and Disease in Antiquity and the Middle Ages

Keywords: Keywords: Crusades, Just war, Lawfulness of war, Saint Augustine, Saint Thomas Aquinas.

In the face of current offensive and preventive wars, based on ideological and economic values, Thomist philosophy and theology are very important, not only in considering the fundamentals of just war, but also applying the theory of private wars as a possible key to giving origin of a new international order. Augustine of Hippo was certainly the creator of the doctrine of just defensive war based on Christian principles, but, taken up by Aquinas, it acquired the idea of an offensive holy war, which involves the protection of justice and the honour of God.