John II (1455-1495) of Portugal, sometimes called "the Perfect Prince," ruled during a crucial period in European history that marked the start of the Age of Exploration. From his ascension to the throne in 1481 until his death fourteen years later, John II's royal treasury financed numerous expeditions that mapped out the African coast. Convinced that India lay on the other side of Africa, he even sent explorers overland. To the Portuguese, he was a much loved regent who curbed the power of the nobles, maintained peace with Spain, and became a great patron of Renaissance art.

John II was named after his great-grandfather, who secured Portugal's independence in the 1380s and founded the House of Aviz royal line. By the time of his arrival in May of 1455, alliances with other European royal lines had given the Aviz family English, French, and Spanish blood. His father, King Alfonso V...