The papacy, however, encountered serious obstacles, at first at the very centre of the papal empire, at Rome, where the pope had to contend with the party of communal autonomy for ten years before being able to secure the mastery at Rome. His im mense authority narrowly escaped destruction but a stone's-throw from the Lateran palace ; but the victory finally rested with him, since the Roman people could not dispense with the Roman Church, to which it owed its existence. Reared in the nurture of the pope, the populace of the Tiber renounced its stormy liberty in 1209, and accepted the peace and order that a beneficent mas ter gave ; but when Innocent attempted to extend to the whole of Italy the regime of paternal subjection that had been so suc cessful at Rome, the difficulties of the enterprise surpassed the powers even of a leader of religion. As guardian of Henry VI.'s son Frederick, Innocent was for some time able to conduct the government of the kingdom of the Two Sicilies, but he was entirely unable, either by diplomacy or force of arms, to make Italian unity redound to the exclusive benefit of the Holy See. Nor was his failure due to lack of activity or energy, but rather to the insuperable obstacles in his path—the physical configura tion of Italy, and, above all, the invincible repugnance of the Italian municipalities.
As far as the Empire was concerned, chance at first favoured Innocent. For ten years a Germany weakened and divided by the rivalry of Philip of Swabia and Otto of Brunswick left his hands free to act in Italy, and his pontificate marks a period of comparative quiet in the ardent conflict between pope and emperor which continued throughout the middle ages. Not until 1210, when Otto of Brunswick turned against the pope to whom he owed his crown, was Innocent compelled to open hostilities; and the struggle ended in a victory for the Curia. Frederick II., the new emperor created by Innocent, began by handing over his country to Rome and sacrificing the rights of the empire to the union of the two great authorities of the Christian world. In his dealings with Frederick, Innocent experienced grievous vicissi tudes and disappointments, but finally became master of the situation. One nation only—the France of Philip Augustus—was
able to remain outside the Roman vassalage.
Finally, Innocent III. was more fortunate than his predecessors. and, if he did not succeed in carrying out his projected crusade and recovering the Holy Places, he at least benefited by the Franco-Venetian expedition of 1202. Europe refused to take any direct action against the Muslim, but Latin feudalism, as sembled at Venice, diverted the crusade by an act of formal dis obedience, marched on Constantinople, seized the Greek empire and founded a Latin empire in its place ; and Innocent had to accept the fait accompli. Though condemning it on principle, he turned it to the interests of the Roman Church as well as of the universal Church. With joy and pride he welcomed the Byzantine East into the circle of vassal peoples and kingdoms of Rome bound politically to the see of St. Peter, and with the same emotions beheld the patriarchate of Constantinople at last recognize Roman supremacy. But from this enormous increase of territory and influence arose a whole series of new and difficult problems. The court of Rome had to substitute for the old Greek hierarchy a hierarchy of Latin bishops ; to force the remaining Greek clergy to practise the beliefs and rites of the Roman religion and bow to the supremacy of the pope ; to maintain in the Greco-Latin Eastern Church the necessary order, morality and subordination; to defend it against the greed and violence of the nobles and barons who had founded the Latin Empire ; and to compel the leaders of the new empire to submit to the apostolic power and execute its commands. In his endeavours to carry out the whole of this programme, Innocent III. met with insuperable obstacles and many disappointments. On the one hand, the Greeks were unwilling to abandon their religion and national cult, and scarcely recognized the ecclesiastical supremacy of the papacy. On the other hand, the upstart Latin emperors, far from proving submis sive and humble tools, assumed with the purple the habits and pretensions of the sovereigns they had dispossessed. Nevertheless, Innocent left his successors a much vaster and more stable political dominion than that which he had received from his predecessors, since it comprised both East and West; and his five immediate successors were able to preserve this ascendancy. They even extended the limits of Roman imperialism by converting the pagans of the Baltic to Christianity, and further reinforced the work of ecclesiastical centralization by enlisting in their service a force which had recently come into existence and was rapidly becoming popular—the mendicant orders, and notably the Domin icans and Franciscans. The Roman power was also increased by the formation of the universities—privileged corporations of mas ters and students, which escaped the local power of the bishop and his chancellor only to place themselves under the direction and supervision of the Holy See. Mistress of the entire Chris tian organism, Rome thus gained control of international educa tion, and the mendicant monks who formed her devoted militia lost no time in monopolizing the professorial chairs. Although the ecclesiastical monarchy continued to gain strength, the suc cessors of Innocent III. made less use than he of their immense power. Under Gregory IX. (1227-1241) and Innocent IV. ( 1254) the conflict between the priesthood and the Empire was revived by the enigmatic Frederick II., the polyglot and lettered emperor, the friend of Saracens, the despot who, in youth styled "king of priests," in later years personified ideas that were di rectly opposed to the mediaeval theocracy ; and the struggle lasted nearly 3o years. The Hohenstaufen succumbed to it, and the papacy itself received a terrible shock, which shook its vast empire to the foundations.
Nevertheless, the first half of the 13th century may be regarded as the grand epoch of mediaeval papal history. Supreme in Europe, the papacy gathered into a body of doctrine the decisions given in virtue of its enormous de facto power, and promulgated its collected decrees and oracula to form the immutable law of the Christian world. Innocent III., Honorius III. and Gregory IX. employed their jurists to collect the most important of their rulings, and Gregory's decrees became the definitive repository of the canon law. Besides making laws for the Christendom of the present and the future, these popes employed themselves in giving a more regular form to their principal administrative organ, the offices of the Curia. The development of the Roman chancery is also a characteristic sign of the evolution that was taking place