What difficulties and perplexities must therefore arise from the frequent contests between the Popes and their feudatories, or between the former and their neighbours, out of such associations, is evident. The state in this province actually most independent of Rome was Ferrara.[142] In the beginning of the thirteenth century the Ferrarese had elected Azzo VI. of Este their hereditary ruler, and the investiture granted him by Pope Innocent III. of considerable possessions in Romagna, as well as in the province of Ancona, had given the house much distinction. A century later, in consequence of a family quarrel, Venice attempted to put forth her claims to Ferrara, and Pope Clement V. was obliged to give way. The attempt of the latter to hold the town in the immediate control of the Church, at first successful, soon failed, and the citizens in 1317 recalled the family of Este, who were eleven years later invested with town and territory by Pope John XXII. The imperial fiefs acquired by the lords of Ravenna, from which they received in 1452 the ducal title from the Emperor Frederick III., nineteen years before Pope Paul II. granted it to Borso d’Este for Ferrara, made their position more independent than that of the other Papal feudatories; but certain rights relating to the republic of Venice, as well as the not always friendly neighbourhood on the lower Po, gave rise to complications which might easily become dangerous. Far less great in territory and power were the counts, afterwards dukes, of Urbino;[143] they, with their little land, were in the same political circumstances between Tuscany and Umbria, Romagna and Ancona. Their family was invested by Frederick Barbarossa with the hilly region of Montefeltro, which afterwards formed the north-western part of their state. In the first decade of the thirteenth century they established themselves in Urbino, which was subject to the Papacy, and gradually extended their possessions on both sides of the mountains—to the south by the acquisition of Gubbio and Cagli, to the north at a much later time as far as the Adriatic sea. They were a warlike race which had once given to the contest of Guelphs and Ghibellines a courageous general in Guido of Montefeltro, and had now one of the best and most highly-prized _condottiere_ in Federigo, who assumed the government in 1444, and for whom Pope Sixtus IV. afterwards renewed the ducal title which his brother and predecessor had borne.