The life at St. Sophia was not strict enough for the young monk, who betook himself first to the island monastery of
Tremite San Nicolo in the
Adriatic and in 1053 to the hermits at
Majella in the
Abruzzi. About this time he was brought to the notice of
Pope Leo IX, and it is probable that the pope employed him at Benevento to negotiate peace with the Normans after the fatal
battle of Civitate. Somewhat later Desiderius attached himself to the court of
Pope Victor II at
Florence. There he met two monks of the renowned
Benedictine monastery of
Monte Cassino, with whom he returned in 1055. He joined the community and was shortly afterwards appointed superior of the dependent house at
Capua. In 1057
Pope Stephen IX, who had retained the abbacy of Monte Cassino, came to visit and at Christmas, believing himself to be dying, ordered the monks to elect a new
abbot. Their choice fell on Desiderius. The pope recovered, and, desiring to retain the abbacy during his lifetime, appointed the abbot-designate his
legate for
Constantinople. It was at
Bari, when about to sail for the East, that the news of the pope's death reached Desiderius. Having obtained a safe-conduct from
Robert Guiscard, the Norman Count (later Duke) of
Apulia, he returned to his monastery and was duly installed by Cardinal Humbert on Easter Day 1058.
Pope Nicholas II elevated him into the
cardinalate as the
Cardinal-Deacon of Santi Sergio e Bacco on 6 March 1058. He opted to be the
Cardinal-Priest of Santa Cecilia in 1059. Desiderius rebuilt the church and conventual buildings, perfected the products of the
scriptorium and re-established monastic discipline, so that there were 200 monks in the monastery in his day. On 1 October 1071, the new Basilica of Monte Cassino was consecrated by
Pope Alexander II. Desiderius' reputation brought gifts and exemptions to the abbey. The money was spent on church ornaments, including a great golden altar front from Constantinople adorned with gems and
enamels and "nearly all the church ornaments of Victor II, which had been pawned here and there throughout the city".
Peter the Deacon gives a list of some seventy books Desiderius had copied at Monte Cassino, including works of
Augustine of Hippo,
Ambrose,
Bede,
Basil of Caesarea,
Jerome,
Gregory of Nazianzus and
Cassian, the histories of
Josephus,
Paul Warnfrid,
Jordanes and
Gregory of Tours, the
Institutes and
Novels of
Justinian, the works of
Terence,
Virgil and
Seneca,
Cicero's
De natura deorum, and
Ovid's
Fasti. Desiderius had been appointed
papal vicar for
Campania, Apulia,
Calabria and the
Principality of Beneventum with special powers for the reform of monasteries. So great was his reputation with the Holy See that he "...was allowed by the Roman Pontiff to appoint Bishops and Abbots from among his
Benedictine brethren in whatever churches or monasteries he desired, of those that had lost their patron". Within two years of the consecration of the Cassinese Basilica, Alexander II died and was succeeded by Hildebrand as
Pope Gregory VII. Desiderius was able to call forth the help of the
Normans of southern Italy repeatedly in favour of the Holy See. Already in 1059 he had persuaded Robert Guiscard and
Richard of Capua to become vassals of St. Peter for their newly conquered territories: now Gregory VII immediately after his election sent for him to give an account of the state of Norman Italy and entrusted him with the negotiation of an interview with Robert Guiscard on 2 August 1073, at
Benevento. In 1074 and 1075 he acted as intermediary, probably as Gregory's agent, between the Norman princes themselves, and even when the latter were at open war with the pope, they still maintained the best relations with Monte Cassino. At the end of 1080 Desiderius obtained Norman troops for Gregory. In 1082 he visited the Italian king and future
Holy Roman Emperor Henry IV at
Albano, while the troops of the Imperialist antipope
Clement III were harassing the pope from
Tivoli. In 1083 the peace-loving abbot joined
Hugh of Cluny in an attempt to reconcile pope and emperor, and his proceedings seem to have aroused some suspicion in Gregory's entourage. In 1084, when Rome was in Henry's hands and the pope besieged in
Castel Sant'Angelo, Desiderius announced the approach of Guiscard's army to both emperor and pope. == Papacy ==