In order to elaborate this plot, we must begin with the great Asiatic movement of the seventh century; for this movement acted as a cause of causes to split the Latins from the Greeks, to exalt the Papacy, and to form the Holy Roman Empire. In one of the tribes of Arabia, without heralding, appeared a man, who at the age of forty became a religious prophet, and by the force of genius constructed one of the great religions of the world. Mohammed's religion worked on the ardent Arabian temperament like magic, and engendered a fierce passion for conquest and proselytizing. Tribes cohered, became both a sect and a nation, and swept like wildfire over the west of Asia and the north of Africa. Mohammed died in 632, but his successors, the Caliphs, carried on his work; under the inspiration of the slogan, "Before you is Paradise, behind you the devil and the fire of hell," they advanced from conquest to conquest. Cities and provinces were torn from the Empire. Damascus, Syria, Jerusalem, Mesopotamia, Armenia, Egypt, Rhodes fell in rapid succession; next Africa, bit by bit. Persia was beaten to her knees. Sicily was raided. Twice Constantinople had to fight for life. Naturally Byzantine statesmen felt that some radical step must be taken, or all the remnants of the Empire would be reduced to slavery. A vigorous Emperor, Leo the Isaurian (717-741), took the radical step. It was necessarily religious, for, in Constantinople, political action always took a religious complexion. Leo issued a decree forbidding the use of images in churches and in Christian worship (726). Those in place he ordered broken. He acted no doubt from high motives, thinking to ennoble religion and to arouse patriotism; but his people disagreed with him. In the East riots and civil war broke out. These were suppressed, but discontent and persistent opposition remained. In Italy also the excitement was intense. The country had already been irritated by severe taxation, and when the decree of iconoclasm was published, the image-loving Italians rose in a body. The Pope, as most hurt in conscience by the decree, and in pocket by the taxation, was the natural head of resistance. The Exarch attempted to arrest him, but both Latins and Lombards rallied to his defence. In some places open revolt broke out, and a plot was started to set up another Emperor in place of the wicked iconoclast who polluted the Imperial throne. But the Pope, Gregory II (715-731), was a prudent man, and was not ready to take a step which would deprive Rome of its single defence from the Lombards. He opposed the rebellious plan, but in the matter of maintaining the images he stood like a rock. His successor, Gregory III (731-741), went farther, and took decisive action. He convoked a synod, which expelled every image-breaker from the Church (731). This was tantamount to a direct excommunication of the Emperor, and a declaration of papal independence. The Emperor was powerless to compel obedience. Thus began