[1] A member of the Lombard nobility,[2] Bertharius as a young man made a pilgrimage to Monte Cassino at the time of the abbacy of Bassacius and decided as a result to become a monk.

Bertharius fortified the abbey with massive walls and towers between 856 and 873,[2] while Louis II of Italy conducted various expeditions against the Muslim forces, beating them back temporarily.

[1] In 873, Muslim raids in Campania and Latium resumed, and a band of raiders paid by the Duke of Naples, Athanasius, established a base in the Apennines in 882.

[2] In 883, the monastery was again attacked, and Bertharius was killed along with some other monks at the altar of St. Martin on October 22 of that year in the church of Saint Salvator at the foot of the hill.

[5][6] Bertharius’ body was immediately translated to Monte Cassino and in 1486 moved to the abbatial church there, in front of the tombs of Saints Benedict and Scholastica.