The thirteenth century witnessed many important events in Italy. The Empire, governed from Germany and unable to keep the Italian peninsula under control, came into conflict with the Italian cities which had become independent communes having constitutions which today we would call "democratic ". In 1176 the Italian communes faced Frederick Barbarossa in pitched battle in Legnano and defeated him. The university, however, survived the collapse of its protector. The communes tried to favour the societatis and Bologna University teacher were asked to swear that they would not teach outside the walls of the city. Their job was secure, on the condition that they should limit themselves to teach exclusively at Bologna. This shows that Bologna, even then, and perhaps earlier, had become the goal of many students from all over Europe, drawn by the fame of its teachers. Moreover, the existence of the University brought the commune international prestige. Students in Bologna did not accept the prohibition of migrations : in 1204 Vicenza, in 1215 Arezzo and in 1228 Vercelli, all in turn broke away. The most important secession occurred in 1222, and caused the institution of a university in Padova which was eventually to become, like Bologna, one of the most important places of learning in Italy. In order to withstand the communes, the students formed groups according to their place of origin. In Bologna there were the Citramontanes (Italians, but not Bolognese, such as the Lombards, Tuscans and Romans) and the Ultramontanes (non-Italians, living north of the Alps, such as the French, Spanish, Provençal, English, Picard, Burgundian, Norman, Catalan, Hungarian, Polish, German). These groups, which were called the universitates, were associations of students trying to establish their autonomy by coming to terms with the local power. The thirteenth century was an age of conflict. In Paris, representatives of the mendicant orders, the Franciscans and the Dominicans, entered the university; they were more receptive to new ideas and struggled against traditional teachers. For example, the Dominicans, among whom was Thomas Aquinas, were largely responsible for the introduction of Aristotelian thought into Western Europe. In 1219 Pope Honorius III granted the Archdeacon of Bologna the authority to award university degrees. The students were permitted to secede and the Rectors of their universitates (who were students, not professor) were not obliged to swear to the commune that they would remain in their residence. Amidst a thousand difficulties, and becoming increasingly involved in the political strife of the time, the University struggled for its own independence while the political powers tried to exploit its prestige. In 1224 Federico II, who lived in Sicily and ruled Holy Roman Empire, attempted to set the University of Naples in opposition to Bologna. In 1230 the Commune granted the same rights to foreign students as those possessed by Bolognese citizens, and the students also consented to swear that they would not leave the Studium .