Catechism of the Catholic Church §2305 — excerpt
Earthly peace is the image and fruit of the peace of Christ, the messianic "Prince of Peace." By the blood of his Cross, "in his own person he killed the hostility," he reconciled men with God and made his Church the sacrament of the unity of the human race and of its union with God.
This translation is under copyright, so only the cited words are quoted here. Follow the link for the full text. Translation: English translation of the Catechism of the Catholic Church, 2nd ed. (Libreria Editrice Vaticana), as posted at vatican.va.