This fact was of great importance, for it enabled the Turks to become masters of the inland sea. In 1492 the greater part of the Moors--the descendants of the Arab conquerors of Spain--were expelled from the Peninsula by the conquest of Granada. This event was hailed with joy throughout Christendom, but it had an unexpected and terrible consequence. Flung back into northern Africa, and filled with hatred because of the persecution they had endured, these Moors embarked on a career of piracy directed against Christians. In making common cause with the Turks they supplied the fleets that the Turkish power needed to carry out its schemes of conquest. Apparently the Turks had never taken to salt water as the Arabs had done, but in these Moorish pirates they found fighters on the sea well worthy to stand comparison with their peerless fighters on land, the Janissaries. Between 1492 and 1580, the date of Ali's death, there was a period in which the Moorish corsairs were supreme. It produced three great leaders, each of whom in turn became the terror of the sea: Kheyr ed Din, known as Barbarossa, Dragut, and Ali. It is a curious fact that the first and third were of Christian parentage. So long as the Turk invaded Christian territory by land alone, the Venetians were unconcerned. They made what treaties they could for continuing their trade with communities that had fallen into the conquerors' hands. But when the Turk began to spread out by sea it was inevitable that he must clash with the Venetian, and so there was much fighting. Yet even after a successful naval campaign the emissary of Venice was obliged to come before the Sultan, cap in hand, to beg trading privileges in Turkish territory. Everything in Venetian policy was subordinated to the maintenance of sufficient friendly relations with the Turk to assure a commercial monopoly in the Levant. Although the Moslem peril grew more and more menacing, Venice remained unwilling to join in any united action for the common good of Europe. Of course Venice was not alone in this policy. In 1534 Francis the First, for example, in order to humiliate his rival, Charles V, secretly sent word to Barbarossa of the plans being made against him. Indeed France showed no interest in combating the Turk even at the time when he was at the summit of his power. But Venice, as the dominating naval power, had the means of checking the Turkish invasion if she had chosen to do so. Instead she permitted the control of the Mediterranean to slip from her into the hands of the Moslems with scarcely a blow.