The origin of some of these illegitimate powers can be traced back to the middle of the eleventh century, when the feudal lords found themselves confronted by a new power in the cities in the form of the corporation or guild of artisans who had gradually become conscious of their strength and importance, and had shown their masters that they were to be counted with in the future. The development of this new movement was furthered by the Wars of Investiture, which, while weakening the authority of the bishops, aroused the minds of the citizens, caused them to take an interest in public affairs, and gave them a desire for freedom. In almost every city there were then two bishops, one representing the Empire, the other the Holy See, and each sought to increase the number of his followers for the purpose of overcoming and expelling his rival; hence innumerable concessions, privileges, and franchises were granted the citizens, until finally, when the struggle was brought to a close by the Concordat of Worms, in 1122, almost all the sovereign rights--the regalia--had passed into the hands of the people. Not only were the bishops forced to yield but the Emperor himself, the Countess Matilda, and all the great lords were compelled to acquiesce in the movement which even extended to cities that were independent of any bishop. Henceforth the cities governed themselves and elected their own chiefs or consuls. They, however, did not pretend to be wholly independent of the Empire but readily acknowledged themselves its feudatories. The movement spread throughout Italy, and many of the cities became so powerful that they compelled the feudal lords of the surrounding country to apply for citizenship and to agree to obey the communal statutes. These various elements introduced into the city soon occasioned discord and quarrels, in which bloodshed became frequent; in addition to this intestine warfare, the rivalry between the different communes resulted in continual strife among them. For a time they were left to prey on each other; for, although they were feudatories of the Empire, the Emperors were unable to devote any attention to the affairs of Italy, Germany being torn asunder by the Guelphs, adherents of the house of Bavaria, and the Ghibellines, supporters of the house of Franconia.