See study by F. J. Gossman (1960).
He was born into nobility in France at Lagery (near Châtillon-sur-Marne) and was church-educated. He was archdeacon of Rheims when, under the influence of his teacher Bruno of Cologne, he resigned and entered the monastery of Cluny where he rose to be prior. In 1078, Pope Gregory VII (1073–85) summoned him to Italy and made him Cardinal-bishop of Ostia.
He was one of the most prominent and active supporters of the Gregorian reforms, especially as legate in Germany in 1084, and was among the few whom Gregory VII nominated as possible successors to be Pope. Desiderius, abbot of Monte Cassino, who became Pope Victor III (1086–87), was chosen Pope initially, but, after his short reign, Odo was elected Pope Urban II by acclamation (March 1088) at a small meeting of cardinals and other prelates held in Terracina. He took up the policies of Pope Gregory VII and, while pursuing them with determination, showed greater flexibility, and diplomatic finesse. At the outset, he had to reckon with the presence of the powerful antipope Clement III (1080, 1084–1100) in Rome; but a series of well-attended synods held in Rome, Amalfi, Benevento, and Troia supported him in renewed declarations against simony, lay investiture, and clerical marriages, and a continued opposition to Emperor Henry IV (1050–1106).
In accordance with this last policy, the marriage of the countess Matilda of Tuscany with Guelph of Bavaria was promoted, Prince Conrad was helped in his rebellion against his father and crowned King of the Romans at Milan in 1093, and the Empress (Adelaide or Praxedes) encouraged in her charges against her husband. In a protracted struggle also with Philip I of France (1060–1108), whom he had excommunicated for his adulterous marriage to Bertrade de Montfort, Urban II finally proved victorious.
Urban II had much correspondence with Archbishop Anselm of Canterbury, to whom he extended an order to come urgently to Rome just after the Archbishop's first flight from England, and earlier gave his approval to Anselm's work De Incarnatione Verbi (The Incarnation of the Word).
Urban II's crusading movement took its first public shape at the Council of Piacenza, where, in March 1095, Urban II received an ambassador from the Byzantine Emperor Alexios I Komnenos (1081–1118) asking for help against the Muslims. A great council met, attended by numerous Italian, Burgundian, and French bishops in such vast numbers it had to be held in the open air outside the city. At the Council of Clermont held in November of the same year, Urban II's sermon proved the most effective single speech in European history, as he summoned the attending nobility and the people to wrestle the Holy Land from the hands of the Seljuk Turks:
I, or rather the Lord, beseech you as Christ's heralds to publish this everywhere and to persuade all people of whatever rank, foot-soldiers and knights, poor and rich, to carry aid promptly to those Christians and to destroy that vile race from the lands of our friends. I say this to those who are present, it meant also for those who are absent. Moreover, Christ commands it.
The chronicler Robert the Monk, quotes Urban II as saying that
[...] this land which you inhabit, shut in on all sides by the seas and surrounded by the mountain peaks, is too narrow for your large population; nor does it abound in wealth; and it furnishes scarcely food enough for its cultivators. Hence it is that you murder one another, that you wage war, and that frequently you perish by mutual wounds. Let therefore hatred depart from among you, let your quarrels end, let wars cease, and let all dissensions and controversies slumber. Enter upon the road to the Holy Sepulchre; wrest that land from the wicked race, and subject it to yourselves. [...] God has conferred upon you above all nations great glory in arms. Accordingly undertake this journey for the remission of your sins, with the assurance of the imperishable glory of the Kingdom of Heaven.
Robert further reports:
When Pope Urban had said these [...] things in his urbane discourse, he so influenced to one purpose the desires of all who were present, that they cried out 'It is the will of God! It is the will of God!'. When the venerable Roman pontiff heard that, [he] said: Most beloved brethren, today is manifest in you what the Lord says in the Gospel, 'Where two or three are gathered together in my name there am I in the midst of them.' Unless the Lord God had been present in your spirits, all of you would not have uttered the same cry. For, although the cry issued from numerous mouths, yet the origin of the cry was one. Therefore I say to you that God, who implanted this in your breasts, has drawn it forth from you. Let this then be your war-cry in combats, because this word is given to you by God. When an armed attack is made upon the enemy, let this one cry be raised by all the soldiers of God: It is the will of God! It is the will of God!
Within Fulcher of Chartres account of pope Urban’s speech, there was a promise of remission of sins for who ever took part in the crusade.
All who die by the way, whether by land or by sea, or in battle against the pagans, shall have immediate remission of sins. This I grant them through the power of God with which I am invested. O what a disgrace if such a despised and base race, which worships demons, should conquer a people which has the faith of omnipotent God and is made glorious with the name of Christ! With what reproaches will the Lord overwhelm us if you do not aid those who, with us, profess the Christian religion! Let those who have been accustomed unjustly to wage private warfare against the faithful now go against the infidels and end with victory this war which should have been begun long ago. Let those who for a long time, have been robbers, now become knights. Let those who have been fighting against their brothers and relatives now fight in a proper way against the barbarians. Let those who have been serving as mercenaries for small pay now obtain the eternal reward. Let those who have been wearing themselves out in both body and soul now work for a double honor. Behold! on this side will be the sorrowful and poor, on that, the rich; on this side, the enemies of the Lord, on that, his friends. Let those who go not put off the journey, but rent their lands and collect money for their expenses; and as soon as winter is over and spring comes, let hem eagerly set out on the way with God as their guide.--Potemkin villages (Potemkin villages) 02:17, 12 October 2008 (UTC)
It is disputed whether the famous slogan "God wills it" or "It is the will of God" (deus vult in Latin, Dieu le veut in French) in fact was established as a rallying cry during the council. While Robert the Monk says so, it is also possible that the slogan was created as a catchy propaganda motto afterwards.
Far more subtle than the Crusades, but far more successful over the long run, was Urban II's program of bringing Campania and Sicily firmly into the Catholic sphere, after generations of control from the Byzantine Empire and the Aghlabid and Fatimid emirs in Sicily. His agent in the Sicilian borderlands was the Norman ruler Roger I (1091–1101). In 1098, after a meeting at the Siege of Capua, Urban II bestowed on Roger I extraordinary prerogatives, some of the very same rights that were being withheld from temporal sovereigns elsewhere in Europe. Roger I was to be free to appoint bishops ("lay investiture"), free to collect Church revenues and forward them to the papacy (always a lucrative middle position), and free to sit in judgment on ecclesiastical questions. Roger I was to be virtually a legate of the Pope within Sicily. In re-Christianizing Sicily, seats of new dioceses needed to be established, and the boundaries of sees established, with a church hierarchy re-established after centuries of Muslim domination.
Roger I's consort Adelaide brought settlers from the valley of the Po to colonize eastern Sicily. Roger I as secular ruler seemed a safe proposition, as he was merely a vassal of his kinsman the Count of Apulia, himself a vassal of Rome, so as a well-tested military commander it seemed safe to give him these extraordinary powers, which were later to come to terminal confrontations between Roger I's Hohenstaufen heirs.