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 Archbishop of Ravenna, as pope in opposition to Pope Gregory, whom the Synod considered deposed; Guibert took the name Clement III. Henry recognized Guibert as pope, swearing that he would lead him to Rome, and there receive from his hands the imperial crown. With 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. Henry entered Rome on 21 March 1084, and succeeded in gaining possession of the greater part of the city. Gregory took refuge in Castel Sant'Angelo. On 24 March, Guibert was enthroned as pope in the church of St. John Lateran as Clement III, and on 31 March he crowned Henry IV as Emperor at St. Peter's. However, with news of the approach of the Norman army of Gregory's ally, Robert Guiscard, Duke of Apulia and Calabria, Henry and Guibert abandoned Rome, and, in revenge for Matilda of Tuscany's support of Gregory, Henry ravaged her possessions in Tuscany. Guibert withdrew to Ravenna, where he still held the title of archbishop. His influence, after Henry IV's withdrawal from Italy, was largely concentrated in Ravenna and a few other districts of Northern Italy, but he also retained some support in Rome. Gregory was liberated, but the people were incensed by the excesses of his Norman allies, and he was compelled to leave Rome. He withdrew to Monte Cassino, and later to the castle of Salerno by the sea, in 1084, where he died in the following year, 25 May 1085. The German episcopate stood divided. While bishops of Gregory VII's party 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 continued to be regarded as pope by Henry and his party. Victor III, who was elected after a