Portuguese Monarch. He reigned as King of Portugal from 1481 to 1495. He was the son of King Afonso V and his queen Isabel of Coimbra, princess of Portugal. João II succeeded his father in 1477 when King Afonso V abdicated, and he became king in 1481. As a prince, João II accompanied his father in the campaigns in Northern Africa and was made a knight by him after the victory in Arzila in 1471. In 1473 he married his first cousin, Leonor of Viseu, Princess of Portugal. Even at a young age, he was not popular among the peers of the kingdom since he was immune to external influence and appeared to despise intrigue. The nobles (including and particularly Fernão II, Duke of Braganza) were afraid of his future policies as king. Events proved them right. After the official accession to the throne in 1481, João II took a series of measures to curtail the overgrown power of his aristocracy and to concentrate power on himself. Immediately the nobles started to conspire; João II did nothing but observe. Letters of complaint and pleas to intervene were exchanged between the Duke of Braganza and Queen Isabella I of Castile. In 1483 this correspondence was intercepted by royal spies. The House of Braganza was outlawed, their lands confiscated and the duke executed in Évora. In the following year, the Duke of Viseu, his cousin and brother-in-law, was summoned to the palace and stabbed to death by the king himself for suspicion of a new conspiracy. Many others were executed, murdered or exiled to Castile including the bishop of Évora who was poisoned in prison. The king is reported to have said, concerning the rebellious nobles: "I'm the lord of lords, not the server of servants". After these events, no one in the country dared to defy the king. João II was free to govern as he pleased without any other conspiracies during his reign. João II then restored the policies of Atlantic exploration, reviving the work of his great-uncle, Prince Henriques the Navigator. The Portuguese explorations were his main priority in government, pushing south the known coastal Africa with the purpose of discovering the maritime route to India. During his reign, Diego Cao discovered the Congo River in 1484, Bartolomeu Dias rounded the Cape of Good Hope in 1488 and Alvaro Caminha started the settlement of the São Tomé and Principe Islands. The complete record of the Portuguese exploration voyages is unknown. Much was kept in secret due to competition from neighbouring Castile. The archives of this period were destroyed in the fire after the 1755 Lisbon earthquake. Possibly Portuguese explorers reach the shores of North America before Christopher Columbus. When Columbus applied for Portuguese help, João II refused. According to the historical theory of Portuguese preeminence, Columbus was an inexperienced Atlantic captain, chasing an idea of a shortcut to India that the king knew was wrong, wanting to go to a place João II already knew how to reach; there was no reason to hire him. In 1492, in the service of the Castile and Aragon kingdoms, Columbus discovered the Americas, convinced until his death that he had reached India. With this event, a series of disputes between Portugal and Castile about the ruling of the seas started. Maritime rivalry between them led to the famous Treaty of Tordesillas, signed June 7, 1494. This treaty, which defined the meridian of Tordesillas, stated that Portugal kept the eastern part of the world, and Castile and Aragon were responsible for the exploration of the western half. But the dividing of the world was not the main issue between the Iberian kingdoms. Isabella I of Castile and Fernando II of Aragon had several daughters, but only one feeble male heir - Juan. The oldest daughter, Isabella of Aragon, was married to João II's only son Afonso (1474-91) since childhood. If Juan died without a male heir, as was probable, Afonso would be heir not only of Portugal, but also of Castile and Aragon. This threat to Castilian and Aragonese independence was very real, and the Catholic kings tried every diplomatic tactic to dissolve the wedding. Finally, in 1491, Afonso died of a fall from a horse during a ride in the margin of the Tagus river. After this, Isabella the heiress was no longer married to the enemy, and João II died without leaving male issue on October 25, 1495; he was succeeded on the Portuguese throne by his first cousin Manõel I.