Of noble birth, Dauferi entered the Benedictine monastery of Montecassino, where he changed his name to Desiderius and where in 1058 he succeeded Pope Stephen IX (X) as abbot. His rule at Montecassino marks the monastery’s golden age, for he promoted writing and manuscript illumination, established an important school of mosaic, and radically reconstructed the abbey, considered a major event in the history of Italian architecture. He was made cardinal priest by Pope Nicholas II in 1059 and papal vicar in southern Italy, where he negotiated peace between the Normans and the papacy. Favoured by the cardinals and his predecessor, Gregory VII, Desiderius was chosen pope, but he declined the office, and the year 1085 passed without an election.
On 24th May 1086, the cardinals proclaimed him pope against his will, but before his consecration was completed, supporters of the Holy Roman emperor Henry IV, who had set up the antipope Clement III in 1084, drove him from Rome. Victor retired to Montecassino. In March 1087, Victor convened a synod at Capua and resumed his papal authority. He received belated consecration in St. Peter’s, Rome, on 9th May, but imperial support for Clement made it impossible for Victor to spend more than a few weeks in the city. He dispatched an army to Tunis, where it defeated the Saracens and compelled them to pay tribute to Rome. In August 1087, he held a synod at Benevento that excommunicated Clement and condemned lay investiture. Falling ill at the synod, Victor returned to Montecassino, where he died in September.
Odo was born of noble parents about 1035 in the Champagne region of France. After studies in Soissons and Rheims, he took the position of archdeacon in the diocese of Rheims, at that time the most important metropolis in France. An archdeacon was an ordained cleric appointed by the bishop to assist him in administration; in the Middle Ages it was an office of considerable power. Odo held the position probably from 1055 to 1067. Subsequently he became a monk and then (c. 1070-74) prior superior at Cluny, the most important centre of reform monasticism in Europe in the 11th century. At Rheims and Cluny, Odo gained experience in ecclesiastical policy and administration and made contacts with two important reform groups of his time: the canons regular (clergymen dedicated to the active service of the church, who live a strict life in community) and the monks of Cluny. In 1079 he went to Rome on a mission for his abbot, Hugh of Cluny. While in Rome he was created cardinal and bishop of Ostia (the seaport for Rome) by Gregory VII. In 1084 Gregory VII sent him as papal legate to Germany. During the crisis of Gregory VII’s struggle with Henry IV, the Holy Roman emperor, Odo remained loyal to the legitimate papacy. After Gregory VII’s death in 1085, he also served his successor, Victor III, who died in September 1087. After a long delay, during which the reform cardinals tried unsuccessfully to regain control of Rome from Guibert of Ravenna, who had been named Pope Clement III by Henry IV in 1080, Odo was elected pope in Terracina, south of Rome, on 12th March 1088.
As pope, Urban II found active support for his policies and reforms among several groups: the nobility, whose mentality and interests he knew; the monks; the canons regular, for whom he became patron and legislator; and also, increasingly, the bishops. Urban felt that his most urgent task was to secure his position against the antipope Clement III and to establish his authority as legitimate pope throughout Christendom. He attempted, with moderation and tolerance, to reconcile the church-state traditions of his age with ecclesiastical notions of reform. In practice he pushed the controversial question of lay investiture more into the background while at the same time retaining reform legislation. He thus softened the conflict and permitted a more peaceful discussion of the problems at issue. At the Council of Clermont (France), in 1095, during which he eloquently called the First Crusade, Urban attempted, however, to prevent a further and complete feudalisation of church-state relationships by prohibiting the clergy from taking oaths of fealty to laymen.
Despite Urban’s attempts at reconciliation, it did not prove possible to come to terms with Henry IV or with a large part of the church within the empire. England also remained closed to papal policies of reform and centralisation. Although Urban had been recognised there since 1095, a conflict between Anselm, the theologian who was named archbishop of Canterbury, and King William II strained the relations between Urban and the king. On the other hand, despite a long-standing conflict between Philip I of France and Urban (brought about by the king’s scandalous marriage), France began under this French pope to become the most important support of the medieval papacy. Urban obtained special support in southern Europe: his particularly faithful allies were the Normans of southern Italy and Sicily. In Spain, Urban supported the Christian reconquest of the country from the Moors and carried out the ecclesiastical reorganisation of the country. In southern Italy, southern France, and Spain, kings and princes became vassals of the Roman see and concluded treaties and concordats in feudal form with the pope: by this the temporal rulers sought to secure their independence from more powerful lords, and the pope for his part was able to carry out his reform aims in these territories.
From 1095 Urban was at the height of his success. From this time several important church councils took place: in 1095 at Piacenza, Italy, at which reform legislation was enacted; also in 1095 at Clermont, where Urban preached the First Crusade; in 1098 at Bari, Italy, where he worked for a reunion between Greek Christians and Rome; and in 1099 at Rome, where again reform legislation was passed. Urban’s idea for a crusade and his attempt to reconcile the Latin and Greek churches sprang from his idea of the unity of all Christendom and from his experiences with the struggles against the Muslims in Spain and Sicily. He was, for a while, able to attract the Byzantine emperor Alexius I to his plans but never the Greek Church. Whereas the First Crusade led to military success with the conquest of Jerusalem in 1099, the project for union failed. Urban’s pontificate not only led to a further centralisation of the Roman Catholic Church but also to the expansion of papal administration. It contributed to the development of the Roman Curia, the administrative body of the papacy and to the gradual formation of the College of Cardinals. Urban died in Rome in 1099.
 H. E. J. Cowdrey The Age of Abbot Desiderius: Montecassino, the Papacy and the Normans in the Eleventh and Early Twelfth Centuries, Oxford University Press, 1983 is the best study of Desiderius. The chief source is the Chronicon Cassinense, in Mon. Germ. Hist.: Script., volume VII, reprinted in Patrologia Latina, volume 173; some autobiographical details can be found in his own Dialogues in Patrologia Latina, volume 149. H. R. Mann, The Lives of the Popes, volume VII, London, 1910, pages 218-244 remains useful.
 Robert Somerville and Stephan Kuttner (eds.) Pope Urban II: The Collectio Britannica, and the Council of Melfi (1089), Oxford University Press, 1996 is a useful study of an important event based on contemporary sources. Alfons Becker Papst Urban II (1088-1099), two volumes, Stuttgart 1964, 1988.