INNOCENT IV. (Sinibaldo Fiesco), pope 1243-54, belonged to the noble Genoese family of the counts of Lavagna. Born at Genoa, he was educated under the care of his uncle Opizo, bishop of Parma. After taking orders at Parma, when he was made canon of the cathedral, he studied jurisprudence at Bologna. His first recorded appearance in political affairs was in 1218-19, when he was associated with Cardinal Hugolinus (afterwards Gregory IX.) in negotiating a peace between Genoa and Pisa. In 1223 Pope Honorius III. gave him a benefice in Parma, and in 1226 he was established at the curia as auditor contradictarum literarum of the pope, a post he held also under Gregory IX., until promoted (12 2 7) to be vice-chancellor of the Roman Church. In September of the same year he was created cardinal priest of San Lorenzo in Lucina. He was papal rector (governor) of the March of Ancona from 1235 to 1240. On June 25, 1243, he was elected pope by the cardinals assembled at Anagni.
When Innocent was raised to the Holy See the emperor Frede rick II. lay under excommunication. Frederick hoped great things from the elevation of a member of an imperialist family; but it was soon clear that Innocent intended to pursue the traditions of his predecessors. Embassies and courtesies were, indeed, inter changed, and on March 31, 1244, a treaty was signed at Rome, whereby the emperor undertook to satisfy the pope's claims in return for his own absolution from the ban. Neither side, however, was prepared to begin to carry out the agreement, and Innocent began to feel unsafe in Rome, where the imperial partisans had the ascendancy. He left Rome, ostensibly to meet the emperor, and from Sutri fled by night on horseback, pursued by the em peror's cavalry, to Civitavecchia, whence he took ship for Genoa and proceeded to Lyons, at that time a merely nominal dependence of the empire. Thence he wrote to Louis IX., asking for an asylum in France; but this Louis cautiously refused. From Lyons Inno cent issued a summons to a general council, before which he cited Frederick to appear in person, or by deputy. The council, which met on June 5, 1245, was attended only by partisans of the pope; and though Frederick condescended to be represented by his justiciar, Thaddeus of Suessa, the judgment was a foregone con clusion.
On July 17, Innocent formally renewed the sentence of excom munication on the emperor, and declared him deposed from the imperial throne and that of Naples. Frederick retorted by an nouncing his intention of reducing "the clergy, especially the highest, to a state of apostolic poverty," and by ordaining punish ments for those priests who should obey the papal sentence. Innocent proclaimed a crusade against the emperor and armed his agents, the Franciscan and Dominican friars, with special indul gences for those who should take up the cross against the imperial heretic. At the same time he sought to undermine Frederick's authority in Germany and Italy. In Naples he fomented a con spiracy among the feudal lords; in Germany, at his instigation, the archbishops with a few of the secular nobles in i 246 elected Henry Raspe, landgrave of Thuringia, German king; but the "priests' king" died in the following year, William II., count of Holland, being after some delay, elected by the papal party in his stead.
Innocent's relentless war against Frederick was not supported by the lay opinion of his time. It wrought havoc and misery in Germany, where it increased the already bitter resentment against the priests. The pope's legate was driven from England by threats of personal violence and not even the saintly King Louis IX. of France, though he made several vain attempts to mediate, ap proved the pope's attitude. The failure of the crusade which, in 1248, he led against the Muslims in Egypt, was ascribed to the deflection of money and arms from this purpose to the war against the emperor. Even the clergy were by no means altogether on Innocent's side ; the council of Lyons was attended by but 15o bishops, mainly French and Spanish, and the deputa tion from England, headed by Robert Grossetete of Lincoln and Roger Bigod, came mainly in order to obtain the canonization of Edmund of Canterbury and to protest against papal exactions. Yet Innocent triumphed. His financial position was from the out set strong, for not only had he the revenue from the accustomed papal dues but he received large sums from the powerful religious orders. At first the war went in Frederick's favour ; but the cap ture of Parma by papal partisans (June 16, 1247) turned the scale. Frederick's camp before Parma (the temporary town of Vittoria) was taken and sacked, the imperial insignia being cap tured. From this blow the emperor never recovered; he died on Dec. 13, 125o.
Innocent left Lyons for Italy in April 1251. He continued the struggle with Frederick's son and successor, Conrad IV., who in 1252 descended into Italy, reduced the rebellious cities and claimed the imperial crown. Innocent now offered the crown of Sicily in turn to Richard of Cornwall, Charles of Anjou, and Henry III. of England, the last of whom accepted the doubtful gift for his son Edmund. After Conrad's capture of Naples Innocent feared that Rome itself might fall into the hands of the German king. But Conrad died on May 20, 1254, leaving his infant son Con radin under the pope's guardianship. Innocent posed as the champion of the infant king. He held, indeed, to his bargain with Henry III. and exercised his rights over the Sicilian kingdom by nominating his own relations to its most important offices. Finally, when Manfred, who by Frederick's will had been charged with the government of the two Sicilies, felt obliged to acknowledge the pope's suzerainty, Innocent threw off the mask, ignored Con radin's claims, and on Oct. 24 formally asserted his own claims to Calabria and Sicily. He entered Naples on the 27th; but mean while Manfred had fled and had raised a considerable force; the news of his initial successes reached Innocent as he lay sick, and hastened his end. He died on Dec. 7, 1254, and was succeeded by Alexander IV.
Innocent IV. is comparable to his greater predecessor Innocent III. mainly in the extreme assertion of the papal claims. In some respects he carried on the high traditions of his great predecessors. He admonished Sancho II. of Portugal to turn from his evil courses and, when the king disobeyed, absolved the Portuguese from their allegiance, bestowing the crown on his brother Alphonso. He established an ecclesiastical organization in the newly con verted provinces of Prussia, which he divided into four dioceses; but his attempt to govern the Baltic countries through a legate broke on the opposition of the Teutonic Order, whose rights in Prussia he had confirmed.
It was Innocent IV. who, at the council of Lyons, first bestowed the red hat on the Roman cardinals, as a symbol of their readiness to shed their blood in the cause of the church.
Innocent was a canon lawyer of some eminence. His small work De exceptionibus was probably written before he became pope ; but the Apparatus in quinque libros decretalium, which displays practical sense and a mastery of the materials, was writ ten at Lyons immediately of ter the council. His Apologeticus, a defence of the papal claims against the empire, has been lost. In nocent was also a notable patron of learning ; he encouraged Alex ander of Hales to write his Summa universae theologiae, did much for the universities, notably the Sorbonne, and founded law schools at Rome and Piacenza.
Innocent's letters, the chief source for his life, are collected by E. Berger in Les Registres d'Innocent IV. (3 vols., 1884-87) . For English readers the account in Milman's Latin Christianity, vol. vi. (3rd ed., 1864) is still useful. Full references will be found in Herzog-Hauck, Realencyklo piidie, vol. ix. (i 9o1) .