80 To hope for a decisive change exclusively from the shock of war and its final issue is idle, as experience shows. The hour of victory is an hour of external triumph for the party to whom victory falls, but it is in equal measure the hour of temptation. In this hour the angel of justice strives with the demons of violence; the heart of the victor all to easily is hardened; moderation and farseeing wisdom appear to him weakness; the excited passions of the people, often inflamed by the sacrifices and sufferings they have borne, obscure the vision even of responsible persons and make them inattentive to the warning voice of humanity and equity, which is overwhelmed or drowned in the inhuman cry. "Vae victis, woe to the conquered." There is danger lest settlements and decision born in such conditions be nothing else than injustice under the cloak of justice.
Source: Summi Pontificatus (Vatican.va)