During the Middle Ages, people all over Europe came to believe in the existence of Prester John, or John the Priest, a Christian king in a faraway land who they believed would come to their aid against the Muslims. This legend first took form in the writings of Otto of Freising (FRY-sing; c. 1111-1158), a German bishop and historian, who claimed that Prester John was a descendant of the Magi (MAY-zhy), the wise men who had attended the birth of Jesus. According to Otto, Prester John's armies had conquered the Persians and forced the Muslims to submit to Christianity.
In 1165, a letter supposedly written by Prester John to several European monarchs turned up in Europe. His land, the letter-writer claimed, was a perfect society in which everyone was wealthy, a place where peace and contentment prevailed. Some Europeans believed that this land must be Ethiopia, known to have a Christian king; therefore in 1177, Pope Alexander III sent a letter to Ethiopia's king, asking for his aid against Muslim enemies. The messenger never returned.
Europeans also identified the homeland of Prester John with India, and the king himself with the Mongols. The myth persisted into the 1500s and 1600s, spurring on the voyages of European explorers eager to find the mythical Christian kingdom.
Use the term "the Sudan" to describe a region of some two million square miles south of the Sahara. About the size of the United States west of the Mississippi River, the Sudan runs from the Atlantic coast in the west almost to the Red Sea coast in the east. Its climate is arid, or dry, and farming is difficult, but during the Middle Ages the region became home to a number of wealthy empires.