By the fi fteenth century, people who had been on the fringes of the Indian Ocean/ Mediterranean trading network became more active. From Ming dynasty China, the Ming Yongle emperor (ruled 1403–24) sent seven huge naval expeditions into the Indian Ocean and the Persian Gulf led by Admiral Zheng He (1371–1433), a Muslim from southwestern China. These were designed to gain control over foreign trade with China and convince people of Chinese power. These expeditions reached the Philippines, the east coast of Africa, and the Red Sea, but the voyages cost far more than the value of the goods brought back. After Zheng He and the Yongle emperor died, Chinese emperors and offi cials became more concerned about land attacks from the Mongols than about demonstrating Chinese power overseas, and sent no more expeditions. At almost the same time that the Yongle emperor sent Zheng He on his voyages, the younger son of the king in a tiny country on the far western end of the Mediterranean also decided to increase his country’s infl uence. Prince Henry of Portugal (1394–1460), later dubbed Prince Henry the Navigator, supported Portuguese explorations down the west African coast and military expeditions against Muslim forces in North Africa. When he was only twenty-one, he conquered the Muslim city of Ceuta in Morocco and became its governor. He learned about the land routes between Ceuta and central Africa, but thought that going by sea might provide better and more direct supplies of gold and slaves. Henry eventually planned and raised the money for over fi fty voyages, and also supported map-makers, astronomers, and mathematicians, who made charts and calculations to assist ships’ captains. Along with searching for gold and slaves, Portuguese captains were also hoping to connect with the Christian kingdom of “Prester John” reported to be somewhere in Africa. Prester (short for presbyter, or priest) John was a mythical Christian ruler fi rst mentioned in European sources in the twelfth century, thought to be a descendant of one of the three kings from the East who presented gifts at the birth of Jesus. About 1165, a letter supposedly written by him to the Byzantine emperor began to circulate in Europe; hundreds of copies in different languages still exist, so many people certainly read it. In the letter, John describes himself as the fabulously wealthy and powerful ruler of a kingdom of Christians in central Asia, whose kingdom was fi lled with fantastic animals as well as “men with horns, one-eyed men, men with eyes before and behind, centaurs, fauns, satyrs, pygmies … [and] some people subject to us who feed on the fl esh of men.” European geographical knowledge of “the Indies” was vague, and the exact location of his kingdom was unclear; over the next several centuries it was thought to be in Mongolia, Persia, India, or Armenia, and the world map of 1507 that fi rst used the word “America” put the kingdom of Prester John in the Himalayas. At the same time, other sources identifi ed the king of Ethiopia (or Abyssinia) as Prester John. Abyssinia had become Christian by the fourth century, and many people there remained Christian after the spread of Islam in Africa, so that the ruler of Abyssinia was actually a better possibility as the heir to Prester John than any ruler in Asia. Portuguese explorers carried letters of introduction to Prester John with them on their voyages along the African coast, and thought they had reached his kingdom when they later reached Ethiopia after sailing around Africa. The story of Prester John is based not on historical evidence about Ethiopian or Asian rulers, however, but on wishful thinking. Though the location of this kingdom varied, its key quality was always a willingness to unite with Christian Europeans against Islam. With the support of Henry and later kings of Portugal, colonies were established on many of the Atlantic islands, including the Azores, the Canaries, the Cape Verde Islands, Madeira, and São Tomé, where Portuguese and Italian investors obtained charters from the Portuguese king to grow and process sugar. Portuguese captains sailed further and further down the African coast, making contacts with rulers in Mali and the Kongo to provide gold and slaves. They used new types of ships, called caravels, which carried several different types of sails, and new instruments, including compasses, astrolabes, and log lines. These tools for navigation were not very accurate, but in experienced hands they allowed mariners to feel secure sailing far out of sight of land, which they had to do on their return voyage back to Portugal because of the wind patterns. The most important motivation for Portuguese voyages was trade with Africa, but they were also trying to fi nd a sea route to the Indian Ocean that would allow them to buy spices directly and avoid Arab, Ottoman, and Italian middlemen. In 1488, Bartolomeu Dias (1450 ?–1500) rounded the southern tip of Africa, but his tired sailors forced him to return to Portugal. In 1497, the Portuguese king Manuel I sponsored a fl eet of four ships under the command of Vasco da Gama ( 1469?–1524), equipped with the best new technology and astronomical charts developed by Prince Henry’s scholars. Da Gama’s ships rounded Africa and sailed up its east coast until they reached towns where they could fi nd mariners with experience in the Indian Ocean. Da Gama hired an Indian ship’s pilot to navigate, and reached Calicut on the west coast of India by sailing directly across the Arabian Sea. Indian and Arabic merchants who were already there resisted da Gama, and he left for Portugal with fewer spices than he had hoped, though King Manuel I still rewarded him richly and gave him the title “Admiral of the Indian Ocean.” Manuel sent da Gama back three years later to enforce Portuguese interests, this time with twenty warships; da Gama bombarded Calicut, defeated an Indian fl eet, and conquered the city. Returning to Portugal with a huge amount of spices, gold, jewels, and other plunder, he was made a count. These riches, and the profits of Portuguese ventures on the west coast of Africa, meant that the Portuguese experience was the opposite of Zheng He’s voyages, and Portuguese rulers had no doubts about whether they should keep sending more.