[Sidenote: Struggle of Frederick with the Papacy.]
Placed as the Empire was, it was scarcely possible for its head not to be involved in war with the constantly aggressive Popedom--aggressive in her claims of territorial dominion in Italy as well as of ecclesiastical jurisdiction throughout the world. But it was Frederick's peculiar misfortune to have given the Popes a hold over him which they well knew how to use. In a moment of youthful enthusiasm he had taken the cross from the hands of an eloquent monk, and his delay to fulfil the vow was branded as impious neglect. Excommunicated by Gregory IX for not going to Palestine, he went, and was excommunicated for going: having concluded an advantageous peace, he sailed for Italy, and was a third time excommunicated for returning. To Pope Gregory he was at last after a fashion reconciled, but with the accession of Innocent IV the flame burst out afresh. Upon the special pretexts which kindled the strife it is not worth while to descant: the real causes were always the same, and could only be removed by the submission of one or other combatant. Chief among them was Frederick's possession of Sicily. Now were seen the fruits which Barbarossa had stored up for his house when he gained for Henry his son the hand of the Norman heiress. Naples and Sicily had been for some two hundred years recognized as a fief of the Holy See, and the Pope, who felt himself in danger while encircled by the powers of his rival, was determined to use his advantage to the full and make it the means of extinguishing imperial authority throughout Italy. But although the struggle was far more of a territorial and political one than that of the previous century had been, it reopened every former source of strife, and passed into a contest between the civil and the spiritual potentate. The old war-cries of Henry and Hildebrand, of Barbarossa and Alexander, roused again the unquenchable hatred of Italian factions: the pontiff asserted the transference of the Empire as a fief, and declared that the power of Peter, symbolized by the two keys, was temporal as well as spiritual: the Emperor appealed to law, to the indelible rights of Cæsar; and denounced his foe as the antichrist of the New Testament, since it was God's second vicar whom he was resisting. The one scoffed at anathema, upbraided the avarice of the Church, and treated her soldiery, the friars, with a severity not seldom ferocious. The other solemnly deposed a rebellious and heretical prince, offered the imperial crown to Robert of France, to the heir of Denmark, to Haco the Norse king; succeeded at last in raising up rivals in Henry of Thuringia and William of Holland. Yet throughout it is less the Teutonic Emperor who is attacked than the Sicilian king, the unbeliever and friend of Mohammedans, the hereditary enemy of the Church, the assailant of Lombard independence, whose success must leave the Papacy defenceless. And as it was from the Sicilian kingdom that the strife chiefly arose, so was the possession of the Sicilian kingdom a source rather of weakness than of strength, for it distracted Frederick's forces and put him in the false position of a liegeman resisting his lawful suzerain. Truly, as the Greek proverb says, the gifts of foes are no gifts, and bring no profit with them. The Norman kings were more terrible in their death than in their life: they had sometimes baffled the Teutonic Emperor; their heritage destroyed him.