During the next four years, the emperor and the pope reconciled but then quarreled again, and, facing a rebellion among the German nobles, Emperor Henry threatened to depose Pope Gregory. Carrying out his threats, Henry summoned his German and Transpadine partisans to a Synod at
Brixen in June, 1080, which drew up a new decree purporting to depose Pope Gregory VII, and which Henry himself also signed, and then proceeded to elect Guibert, the excommunicated simoniacal Archbishop of Ravenna, as antipope in opposition to Pope Gregory; Guibert took the name Clement III. Henry at once recognized Guibert as pope, swearing that he would lead him to Rome, and there receive from his hands the imperial crown.
The antipope failed to secure recognition outside of Henry's dominions and was widely understood as being merely his puppet and quite devoid of personal initiative.
Rudolph of Swabia, leader of the rebellious nobles, having fallen mortally wounded at the
Battle of Mersburg in
1080, Henry could concentrate all his forces against Gregory. In 1081 he marched on Rome, but failed to force his way into the city, which he finally accomplished only in 1084.
Gregory thereupon retired into the citadel of Sant' Angelo, and refused to entertain Henry's overtures, although the latter promised to hand over Guibert as a prisoner, if the Pope would only consent to crown him emperor.
Gregory, however, insisted as a necessary preliminary that Henry should appear before a council and do penance. The emperor, while pretending to submit to these terms, tried hard to prevent the meeting of the bishops. A small number however assembled, and, in accordance with their wishes, Gregory again excommunicated Henry.
The latter on receipt of this news again entered Rome on
March 21, 1084, and succeeded in gaining possession of the greater part of the city and besieged the Pope in the Castle of Sant' Angelo, while, on
March 24, Guibert was enthroned as pope in the church of
St. John Lateran as Clement III, and on
March 31 Guibert crowned Henry IV emperor at St. Peter's.
However, when the news was brought that Gregory's
Norman ally,
Robert Guiscard, Duke of Normandy, was hastening to his aid, Henry fled Rome with Guibert and, in revenge for Matilda's staunch support for Gregory and the reform party, ravaged her possessions in
Tuscany.
The Pope was liberated, but, the people becoming incensed by the excesses of his Norman allies, he was compelled to leave Rome. Disappointed and sorrowing he withdrew to
Monte Cassino, and later to the castle of
Salerno by the sea, in
1084, where he died in the following year,
May 25, 1085.
Three days before his death he withdrew all the censures of excommunication that he had pronounced, except those against the two chief offenders Henry and Guibert. His last words were:
:
"I have loved justice and hated iniquity, therefore I die in exile."
The German
episcopate stood divided. While anti-simonical bishops held a Synod in
Quedlinburg, at which they denounced and condemned Guibert, partisans of Henry held a rival Synod at
Mainz in 1085, where they approved the deposition of Gregory and the elevation of Guibert.
This conflict continued even after the death of Gregory, during the entire reigns of whose successors,
Pope Victor III, Pope Urban II, and
Pope Paschal II, Guibert figured as the antipope of Henry and his party.
Victor III, who was elected after a prolonged vacancy caused by the critical position of the Church in Rome, was compelled, eight days after his coronation in St. Peter's on
May 3, 1087, to fly from Rome before the partisans of Guibert. The latter were in turn assailed by the troops of Countess Matilda, and entrenched themselves in the Pantheon.
The succeeding pope, Urban II (1088-1099), was at one time master of Rome, but he was afterwards driven from the city by the adherents of Guibert, and sought refuge in Lower Italy and in France.
In June, 1089, at a Synod held in Rome, the antipope declared invalid the decree of excommunication launched against Henry, and various charges were made against the supporters of the legitimate pope.
Still, the years which followed brought to Urban ever-increasing prestige, while Henry IV's power and influence were more and more on the wane.
The greater part of the city of Rome was captured by an army of crusaders under Count
Hugh of Vermandois, brother of the
King of France. The party of Guibert retained only the Castle of Sant' Angelo, and even this in 1098 fell into the hands of Vermandois.
Guibert's influence, after Henry IV's withdrawal from Italy, was virtually confined to Ravenna and a few other districts of Northern Italy.
In 1099, he repaired to
Albano after the accession of Paschal II (1099-1118), hoping again to become master of Rome, but he was compelled to withdraw. He reached Cività Castellana, where he died
September 8, 1100. His followers, it is true, elected a successor to Guibert, the
Antipope Theodoric, who, however, was not a serious threat to the true popes.
The elevation of Guibert has to be seen in the wider context of the time: there had been several antipopes in the recent past, there were political struggles within the empire, and the
Investiture Crisis also had an effect.
Clement was notoriously regarded as the champion of the simoniacal and anti-celibacy and pro-clerical concubinage party, although he went through the notions of legislating against these abuses, and, through the leeway he granted the cardinals supporting him, contributed to the development of the
College of Cardinals.
