The confusion of the Catharists, or Catari, with the Patarini probably arose from the similarity of the names, and the natural tendency of the orthodox to confuse the different forms of thought outside their own dogmatic boundaries. The Patarini sympathised with the Catharists only in their practice of purity and evangelic simplicity of life. There is little doubt, however, that the Catharists mingled with the poorer classes of the city whence the Patarini were recruited, and must have taken advantage of the confusion of ideas resulting from the revolt against the old customs and authority to spread their doctrines.

Among the Milanese clergy themselves there was a small party zealous for reform. The first to raise open protest against simony and ‘concubinage’ was one of these, a noble ecclesiastic called Anselmo da Baggio. Ariberto’s vacant throne had been filled by the appointment of one Guido, a creature of the Emperor Henry III., who in securing his election, had partly recovered that sway over Milan which Ariberto had wrested from Conrad. Guido was a weak man, with an uneasy conscience himself about simony, since he had paid the usual fee to the emperor as his feudal superior for the confirmation of his election. Thinking to rid himself of the troublesome zeal of Anselmo, he procured his election to the bishopric of Lucca, and thus endowed him with new power. Anselmo was one of the principal allies and agents of Hildebrand, by whose influence he was raised later to the papal throne, where, as Alexander II., he was able to wield all the arms of Rome against his native Church. Another leader of a more popular class soon rose up to take his place in Milan, a certain deacon and student of letters named Arialdo. This man became the soul of the movement. He was joined by Landolfo da Cotta, one of the highest order of clergy, like Anselmo da Baggio. Landolfo was a fiery and eloquent speaker, a zealot whose body was consumed by disease and his soul by enthusiasm. The two went about preaching in public places and stirring up the poorer classes, and soon gathered together a formidable following. Invading the churches, they drove the clergy from the altars, and pursuing them with contumely and violence, sacked their houses and forced them to sign an engagement to consort no more with women. The whole city was in an uproar; all the sons of disorder rushed to join the rioters. Archbishop Guido summoned a synod of his clergy at a safe distance from the city, and thence fulminated an anathema against the ringleaders. Arialdo and Landolfo immediately hastened to Rome to make their complaint before the throne of Peter (1057). They returned accompanied by the Bishop of Lucca and Cardinal Hildebrand himself, sent by Pope Stephen X. to examine into the accusations laid against the Archbishop and his clergy. Their arrival raised a new and tremendous uproar. The Milanese, deeply jealous of the ancient episcopal glory and prerogatives of their city, rallied to the side of their own clergy at this attempt of the Pope to interfere, and the legates, having hastily and in secret condemned the Archbishop as simoniacal, and all his practices as abominable, departed, leaving matters worse than before.

As soon as the Roman attack had been driven off, and the issue appeared to be confined within the city, the masses again joined Arialdo. The clamour of bells and trumpets filled the streets and called the people to assemble in the great Roman theatre, where Arialdo and Landolfo inflamed their minds to fury by discourses against the clergy. There were daily riots in the streets. The clergy were supported by the nobles and by all the peaceable spirits, who, however, had none of the energy and zeal of their opponents, and soon wearied of the continual disorders and tumults. The struggle continued with intermittent uproar, and two years after the mission of Hildebrand, the Pope made a new attempt at intervention (1059). This time with the Bishop of Lucca there came instead of Hildebrand, whose soul contained no balm to pour upon angry passions, the famous Peter Damian. The contemplative of Fonte Avellana, fierce ascetic as he was, and inflamed with impatience and contempt for luxurious priests, nevertheless possessed the gift of persuading and winning men. The difficulties which had defeated the earlier legation met him also. The Ambrosian clergy stood out for the ancient freedom of their Church and Diocese and the independence of its jurisdiction. Enormous crowds gathered round the episcopal palace, thirsting for the blood of the new representatives of the papal pretensions, and the popular fury rose to a height when at a great assembly which Peter convoked to hear his message he placed the Archbishop of Milan on his left hand, giving the place of pre-eminence on his right to the Bishop of Lucca, as delegate of the Pope. But the sound of his voice calmed the tumult as he rose and eloquently proclaimed the glory of the Ambrosian Church and of the many martyrs who had sanctified it with their blood, and so skilfully and with such moving words did he reprove its abuses, that before long Archbishop, dignitaries and the whole immense throng of clerics, trembling with emotion and penitence, were prostrate before the altar, acknowledging their sinful practices and vowing to renounce them for the future. The success of the preacher was confirmed by the subsequent visit of Archbishop Guido to Rome, in answer to a summons from Nicholas II. There for the first time in history the Primate of Milan was constrained to promise obedience to the Pope of Rome, and to receive from him the symbolic ring of investiture.

This humiliation of their episcopal prince was a bitter grief to the noble party in Milan. Veneranda est Roma in Apostolo. But Milan is not to be despised in Ambrose, cries Arnolfo the chronicler. ‘It will be said in future that Milan is subject to Rome.’ And though Rome had won a lasting advantage, the moral effect of Peter Damian’s mission soon died out. The old ecclesiastical system and usage was not so easily overthrown. Two years later (1061) the conflict was resumed with new fervour by the Patarini, encouraged by the accession of their ally, Anselmo of Lucca, to the Papal throne. Moreover, a new champion of reform had arisen in Erlembaldo, a warrior lately returned from a pilgrimage to the Holy Land, and brother of the now dying Landolfo. Bold as a lion, breathing out fire and slaughter against the Ambrosians, Erlembaldo was a formidable foe for the timid Archbishop and his party, who were inspired by no confidence in the virtue of their cause. He appeared in the arena of conflict bearing the standard of the Church, with which he had been solemnly trusted by Pope Alexander, who did not hesitate to rekindle the flames of civil war in his native city.

The cruel scenes witnessed before were now renewed in Milan. Blood was spilt in the streets, churches were invaded and sacked, priests dragged bodily from the altars, their houses burnt, their wives misused. But when Arialdo and his lieutenant began to condemn the ceremonial usages peculiar to the Ambrosian Church, the citizens turned against them, and finding the opposition too strong, the two missionaries appealed to Rome and procured the excommunication of the Archbishop. This only aggravated the wrath of the Milanese. The Patarine leaders were abandoned by all but a few of their most devoted followers, and when Archbishop Guido appeared before the altar of the Cathedral Church with the Bull of excommunication in his hands, the fury of the immense assembly knew no bounds. The reformers were set upon in the sanctuary itself, and Arialdo was so badly beaten that he was left for dead. Guido, taking advantage of the momentary turn of the tide in his favour, laid an interdict upon the city until it should rid itself of Arialdo. The zealot was forced to fly, and a little later he fell into a snare which had been laid for him, and was betrayed into the hands of the Archbishop’s niece, lady of a castle on Lake Maggiore, by whose command he was carried in a boat to a lonely island and there cruelly done to death.

The cause of reform was thenceforth glorified by the memory and example of a martyr. Arialdo was shortly afterwards canonised by Pope Alexander. His loss inflamed his party to new zeal and drew to it a great access of adherents. Erlembaldo and a priest called Liprando di San Paolo now led the crusade, carrying it on with such fury of sword and fire that they became virtual masters of the city. The Archbishop, wearied out by the endless strife and the insidious attempts of Rome to depose him, renounced his See, and the nobles, outnumbered by the rioters, abandoned the disorderly city and sought peace and safety in their castles and country palaces.

The contest now centred on the election of a new Archbishop. Neither of the rival claimants put forward by the two parties succeeded in establishing himself on the episcopal throne. Chaos prevailed in the Ambrosian Church. Erlembaldo, strengthened by the accession of Hildebrand as Pope Gregory VII., usurped the whole authority in the city and throughout the archdiocese. He swept far and wide like an avenging sword, driving priests from their benefices, and tearing them from the altars. Half Lombardy cowered under his rude and noisy tyranny, and his name became a by-word of terror throughout Italy.

But two appalling conflagrations, which followed one another in 1071 and 1073, and laid waste the city, deprived the people of all heart for the contest with the aristocrats. Moreover, Erlembaldo’s tyranny was beginning to produce a reaction. The nobles, regaining courage, leagued together for a great effort to liberate the city from his authority. By means of promises and gold, they won a large number of the humble citizens to their side, and at last they appeared one day in force in the city, seeking their enemy. The populace, awed by their numbers and magnificent martial array, were little disposed to face them. Followed by a few only of the most faithful and zealous of the Patarini, Erlembaldo, mounted upon his war-horse, and in full armour, upholding the banner of the Roman Church, flung himself into the midst of his foes, and fell, pierced by a hundred swords.

With his death the war ended. There was none to take his place. The city, exhausted by the long strife, was glad to rest. The nobles returned to their homes and their old place in the city, and in spite of the persecution which they had suffered for twenty years, the Ambrosian clergy resumed their old practices to a large extent.

Nevertheless, the design of the great Hildebrand was achieved. The supremacy of Rome had been proclaimed, and acknowledged in the hearing of the whole world. The prestige of the greatest of the provincial Sees had suffered a blow from which it never recovered. So much was the episcopal power of Milan weakened that Gregory VII. was able to subtract many of its suffragan Sees and join them instead to other archdioceses; and before the century was over, the victory of the Pope over the Emperor Henry IV., in the famous quarrel of investitures, obliged the Ambrosian See to yield temporal as well as spiritual allegiance to the successors of St. Peter.