Monastic and Episcopal Career
Peter's career followed the path of Galicia's reformed Benedictine monasticism. After entering Santa Maria de Mezonzo, he moved to the Monastery of Santa Maria de Sobrado, where he was elected abbot in 965. He subsequently governed the monastery of San Paio de Antealtares in Santiago de Compostela; one Spanish account associates his formation with the circle of the bishop and monastic reformer Rosendo.
From this monastic background he was raised to the episcopate, becoming bishop of the see of Iria Flavia, the historic seat that was bound to the great pilgrimage shrine of Santiago de Compostela. He held the office through the closing years of the tenth century until his death in 1003.
The Raid of Almanzor (997)
In 997 the Cordovan military commander Almanzor (Al-Mansur) launched an expedition against Santiago de Compostela, the foremost Christian sanctuary of the Iberian peninsula. When word reached the city of the approaching army, Peter ordered the population to evacuate and withdrew to a monastery in the interior, by tradition Sobrado, taking the relics with him.
The campaign was devastating. According to the historical record, Almanzor's forces reached the city and demolished the cathedral, the monastery of San Martin Pinario, the monastery of Antealtares, the local hospital, and the other temples and palaces; the cathedral bells and doors were carried off by captives to Cordoba, where the bells were repurposed as lamps for the great mosque. Yet the tomb of the Apostle James was deliberately spared, and guards posted by Almanzor prevented it from being harmed. A widespread tradition relates that Almanzor came upon the aged bishop praying at the Apostle's tomb and, moved by his devotion, ordered the sepulcher left untouched. Two years after the raid, Peter is credited with beginning the restoration of the shrine of Santiago.
Attribution of the Salve Regina
By a long-standing Galician tradition, Peter of Mozonzo is named as the author of the Salve Regina, one of the best-known Marian antiphons of the Latin Church. The sources that record this attribution are careful to frame it as devotional tradition rather than documented fact; one notes plainly that scholarly verification is absent, and others present the composition as legend.
Where the tradition is elaborated, the hymn is said to have been inspired by the image of Nuestra Senora de los Ojos Grandes (Our Lady of the Great Eyes), the patroness of Lugo, and composed amid the dangers facing Galicia in the saint's lifetime.