For more than a century after the death of Gregory the Great his successors continued to remain respectful subjects of the emperor. They looked to him for occasional help against the Lombards in northern Italy, who showed a disposition to add Rome to their possessions. In 725, however, the emperor Leo III aroused the bitter opposition of the pope by issuing a decree forbidding the usual veneration of the images of Christ and the saints. The emperor was a thoughtful Christian and felt keenly the taunts of the Mohammedans, who held all images in abhorrence and regarded the Christians as idolaters. He therefore ordered all sacred images throughout his empire to be removed from the churches, and all figures on the church walls to be whitewashed over. This aroused serious opposition even in Constantinople, and the farther west one went, the more obstinate became the resistance. The pope refused to obey the edict, for he held that the emperor had no right to interfere with practices hallowed by the Church. He called a council which declared all persons excommunicated who should "throw down, destroy, profane or blaspheme the holy images." The opposition of the West was successful, and the images kept their places.[38] [Sidenote: The popes and the Lombards.] [Sidenote: The pope turns to the Franks for aid.] In spite of their abhorrence of the iconoclastic Leo and his successors, the popes did not give up all hope that the emperors might aid them in keeping the Lombards out of Rome. At last a Lombard ruler arose, Aistulf, a "son of iniquity," who refused to consider the prayers or threats of the head of the Church. In 751 Aistulf took Ravenna and threatened Rome. He proposed to substitute his supremacy for that of the eastern emperor and make of Italy a single state, with Rome as its capital. This was a critical moment for the peninsula. Was Italy, like Gaul, to be united under a single German people and to develop, as France has done, a characteristic civilization? The Lombards had progressed so far that they were not unfitted to organize a state that should grow into a nation. But the head of the Church could not consent to endanger his independence by becoming the subject of an Italian king. It was therefore the pope who prevented the establishment of an Italian kingdom at this time and who continued for the same reason to stand in the way of the unification of Italy for more than a thousand years, until he was dispossessed of his realms not many decades ago by Victor Emmanuel. After vainly turning in his distress to his natural protector, the emperor, the pope had no resource but to appeal to Pippin, upon whose fidelity he had every reason to rely. He crossed the Alps and was received with the greatest cordiality and respect by the Frankish monarch, who returned to Italy with him and relieved Rome (754). [Sidenote: Pippin subdues the Lombards.]