In the year 1059 this had been changed. By a decree of Pope Nicholas II the principal priests and deacons of the churches in and around Rome were organised into the so-called College of Cardinals, and this gathering of prominent churchmen (the word "Cardinal" meant principal) was given the exclusive power of electing the future Popes.
In the year 1073 the College of Cardinals elected a priest by the name of Hildebrand, the son of very simple parents in Tuscany, as Pope, and he took the name of Gregory VII. His energy was unbounded. His belief in the supreme powers of his holy office was built upon a granite rock of conviction and courage. In the mind of Gregory, the Pope was not only the absolute head of the Christian church, but also the highest Court of Appeal in all worldly matters. The Pope who had elevated simple German princes to the dignity of Emperor could depose them at will. He could veto any law passed by duke or king or emperor, but whosoever should question a papal decree, let him beware, for the punishment would be swift and merciless.
Gregory sent ambassadors to all the European courts to inform the potentates of Europe of his new laws and asked them to take due notice of their contents. William the Conqueror promised to be good, but Henry IV, who since the age of six had been fighting with his subjects, had no intention of submitting to the Papal will. He called together a college of German bishops, accused Gregory of every crime under the sun and then had him deposed by the council of Worms.
The Pope answered with excommunication and a demand that the German princes rid themselves of their unworthy ruler. The German princes, only too happy to be rid of Henry, asked the Pope to come to Augsburg and help them elect a new Emperor.
Gregory left Rome and travelled northward. Henry, who was no fool, appreciated the danger of his position. At all costs he must make peace with the Pope, and he must do it at once. In the midst of winter he crossed the Alps and hastened to Canossa where the Pope had stopped for a short rest. Three long days, from the 25th to the 28th of January of the year 1077, Henry, dressed as a penitent pilgrim (but with a warm sweater underneath his monkish garb), waited outside the gates of the castle of Canossa. Then he was allowed to enter and was pardoned for his sins. But the repentance did not last long. As soon as Henry had returned to Germany, he behaved exactly as before. Again he was excommunicated. For the second time a council of German bishops deposed Gregory, but this time, when Henry crossed the Alps he was at the head of a large army, besieged Rome and forced Gregory to retire to Salerno, where he died in exile. This first violent outbreak decided nothing. As soon as Henry was back in Germany, the struggle between Pope and Emperor was continued.