In 1383, John I of Castile, husband of Beatrice of Portugal and son-in-law of Ferdinand I of Portugal, claimed the throne of Portugal. A faction of petty noblemen and commoners, led by John of Aviz (later King John I of Portugal) and commanded by General Nuno Álvares Pereira defeated the Castilians in the Battle of Aljubarrota. With this battle, the House of Aviz became the ruling house of Portugal.

The new ruling dynasty would proceed to push Portugal to the limelight of European politics and culture, creating and sponsoring works of literature, like the Crónicas d'el Rei D. João I by Fernão Lopes, the first riding and hunting manual Livro da ensinança de bem cavalgar toda sela and O Leal Conselheiro both by King Edward of Portugal and the Portuguese translations of Cicero's De Oficiis and Seneca's De Beneficiis by the well traveled Prince Peter of Coimbra, as well as his magnum opus Tratado da Vertuosa Benfeytoria. In an effort of solidification and centralization of royal power the monarchs of this dynasty also ordered the compilation, organization and publication of the first three compilations of laws in Portugal: the Ordenações d'el Rei D. Duarte, which was never enforced; the Ordenações Afonsinas, whose application and enforcement was not uniform across the realm; and the Ordenações Manuelinas, which took advantage of the printing press to reach every corner of the kingdom. The Avis Dynasty also sponsored works of architecture like the Mosteiro da Batalha (literally, the Monastery of the Battle) and led to the creation of the manueline style of architecture in the 16th century.

Portugal also spearheaded European exploration of the world and the Age of Discovery. Prince Henry the Navigator, son of King John I of Portugal, became the main sponsor and patron of this endeavour. During this period, Portugal explored the Atlantic Ocean, discovering the Atlantic archipelagos the Azores, Madeira, and Cape Verde; explored the African coast; colonized selected areas of Africa; discovered an eastern route to India via the Cape of Good Hope; discovered Brazil, explored the Indian Ocean, established trading routes throughout most of southern Asia; and sent the first direct European maritime trade and diplomatic missions to China and Japan.

In 1415, Portugal acquired the first of its overseas colonies by conquering Ceuta, the first prosperous Islamic trade centre in North Africa. There followed the first discoveries in the Atlantic: Madeira and the Azores, which led to the first colonization movements.

In 1422, by decree of King John I, Portugal officially abandoned the previous dating system, the Era of Caesar, and adopted the Anno Domini system, therefore becoming the last catholic realm to do so.


Throughout the 15th century, Portuguese explorers sailed the coast of Africa, establishing trading posts for several common types of tradable commodities at the time, ranging from gold to slaves, as they looked for a route to India and its spices, which were coveted in Europe.

The Treaty of Tordesillas, intended to resolve the dispute that had been created following the return of Christopher Columbus, was made by Pope Alexander VI, the mediator between Portugal and Spain. It was signed on 7 June 1494, and divided the newly discovered lands outside Europe between the two countries along a meridian 370 leagues west of the Cape Verde islands (off the west coast of Africa).


In 1498, Vasco da Gama accomplished what Columbus set out to do and became the first European to reach India by sea, bringing economic prosperity to Portugal and its population of 1.7 million residents, and helping to start the Portuguese Renaissance. In 1500, the Portuguese explorer Gaspar Corte-Real reached what is now Canada and founded the town of Portugal Cove-St. Philip's, Newfoundland and Labrador, long before the French and English in the 17th century, and being just one of many Portuguese colonizations of the Americas.

In 1500, Pedro Álvares Cabral discovered Brazil and claimed it for Portugal. Ten years later, Afonso de Albuquerque conquered Goa in India, Muscat and Ormuz in the Persian Strait, and Malacca, now a state in Malaysia. Thus, the Portuguese empire held dominion over commerce in the Indian Ocean and South Atlantic. Portuguese sailors set out to reach Eastern Asia by sailing eastward from Europe, landing in such places as Taiwan, Japan, the island of Timor, and in the Moluccas.

Although for a long period it was believed the Dutch were the first Europeans to arrive in Australia, there is also some evidence that the Portuguese may have discovered Australia in 1521. From 1519 to 1522, Ferdinand Magellan (Fernão de Magalhães) organized a Spanish expedition to the East Indies which resulted in the first circumnavigation of the globe. Magellan never made it back to Europe as he was killed by natives in the Philippines in 1521.

The Treaty of Zaragoza, signed on 22 April 1529 between Portugal and Spain, specified the anti-meridian to the line of demarcation specified in the Treaty of Tordesillas.

All these factors made Portugal one of the world's major economic, military, and political powers from the 15th century until the late 16th century.
What was the The Treaty of Tordesillas?
After Christopher Columbus returned, a dispute arose between Portugal and Spain, which Pope Alexander VI mediated for the Treaty of Tordesillas.
According to this joint treaty, the newly discovered lands beyond Europe are divided between the two countries along a meridian located 370 leagues west of the Cape Verde islands.