To his naval training-station at Sagres and the neighboring port of Lagos, Prince Henry attracted the most skillful Italian navigators and the most learned geographers of the day. The expeditions which he sent out year after year rediscovered and colonized the Madeira and Azores Islands, and crept further and further down the unknown coast of the Dark Continent. When in the year 1445, a quarter of a century after the initial efforts of Prince Henry, Denis Diaz reached Cape Verde, he thought that the turning point was at hand; but four more weary decades were to elapse before Bartholomew Diaz, in 1488, attained the southernmost point of the African coast. What he then called the Cape of Storms, King John II of Portugal in a more optimistic vein rechristened the Cape of Good Hope. Following in the wake of Diaz, Vasco da Gama rounded the Cape in 1497, and then, continuing on his own way, he sailed up the east coast to Malindi, where he found a pilot able to guide his course eastward through the Indian Ocean to India. At Calicut Vasco da Gama landed in May, 1498, and there he erected a marble pillar as a monument of his discovery of a new route to the Indies. [Sidenote: Occupation of Old Trade-Routes by the Turks] While the Portuguese were discovering this new and all-water route to the Indies, the more ancient Mediterranean and overland routes, which had been of inestimable value to the Italians, were in process of occupation by the Routes by Ottoman Turks. [Footnote: Professor A. H. Lybyer has recently and ably contended that, contrary to a view which has often prevailed, the occupation of the medieval trade-routes by the Ottoman Turks was not the cause of the Portuguese and Spanish explorations which ushered in the Commercial Revolution. He has pointed out that prior to 1500 the prices of spices were not generally raised throughout western Europe, and that apparently before that date the Turks had not seriously increased the difficulties of Oriental trade. In confirmation of this opinion, it should be remembered that the Portuguese had begun their epochal explorations long before 1500 and that Christopher Columbus had already returned from "the Indies."] These Turks, as we have seen, were a nomadic and warlike nation of the Mohammedan faith who "added to the Moslem contempt for the Christian, the warrior's contempt for the mere merchant." Realizing that advantageous trade relations with such a people were next to impossible, the Italian merchants viewed with consternation the advance of the Turkish armies, as Asia Minor, Thrace, Macedonia, Greece, and the islands of the Ægean were rapidly overrun. Constantinople, the heart of the Eastern Empire, repeatedly repelled the Moslems, but in 1453 Emperor Constantine XI was defeated by Sultan Mohammed II, and the crescent replaced the Greek cross above the Church of Saint Sophia. Eight years later Trebizond, the terminal of the trade-route from Tabriz, was taken.