His love for knowledge and culture was passed to his sons, often collectively referred to by Portuguese historians as the "illustrious generation" (Ínclita Geração): Edward, the future king, was a poet and a writer; Peter, the Duke of Coimbra, was one of the most learned princes of his time; and Prince Henry the Navigator, the duke of Viseu, invested heavily in science and the development of nautical pursuits.

In 1430, John's only surviving daughter, Isabella, married Philip the Good, Duke of Burgundy, and enjoyed an extremely refined court culture in his lands; she was the mother of Charles the Bold.

Failing to take the city in a series of assaults, the Portuguese siege camp was soon itself surrounded and starved into submission by a Moroccan relief army.

In the resulting treaty, Henry promised to deliver Ceuta back to the Marinids in return for allowing the Portuguese army to depart unmolested.

Meanwhile, colonization progressed in the Azores and Madeira, where sugar and wine were now produced; above all, the gold brought home from Guinea stimulated the commercial energy of the Portuguese.

Under Afonso V (1443–1481), surnamed the African, the Gulf of Guinea was explored as far as Cape St Catherine (Cabo Santa Catarina),[4] [5] [6] and three expeditions (1458, 1461 and 1471) were sent to Morocco; in 1471 Arzila and Tangier were captured from the Moors.

The treaty gave to Portugal all lands that might be discovered east of a straight line drawn from the Arctic Pole to the Antarctic, at a distance of 370 leagues west of Cape Verde.

The known means of measuring longitude were so inexact, however, that the line of demarcation could not in practice be determined (see J. de Andrade Corvo in Journal das Ciências Matemáticas, xxxi.147–176, Lisbon, 1881), so the treaty was subject to very diverse interpretations.

Several historians have hypothesized that John II may have known of the existence of Brazil and North America as early as 1480, thus explaining his wish in 1494 at the signing of the Treaty of Tordesillas to push the line of influence further west.

Unfortunately, due to the fire following the earthquake of 1755, nearly all of the library's records were destroyed,[citation needed] but an extra copy available in Goa was transferred to Lisbon Tower of Tombo during the following 100 years.

The Corpo Cronológico (Chronological Corpus), a collection of manuscripts on the Portuguese explorations and discoveries in Africa, Asia and Latin America, was inscribed on UNESCO’s Memory of the World Register in 2007 in recognition of its historical value "for acquiring knowledge of the political, diplomatic, military, economic and religious history of numerous countries at the time of the Portuguese Discoveries.

After the death of Edward, further attempts to curb the power of the nobles were made by his brother, D. Pedro, duke of Coimbra, who acted as regent during the minority of Afonso V of Portugal (1439–1448).

In 1479 Ferdinand and Isabella and Afonso signed the Treaty of Alcáçovas, by which Joanna was relegated to a convent and Portugal won the hegemony in the Atlantic Ocean.

Finding, as he said, that the liberality of former kings had left the Crown "no estates except the high roads of Portugal," he determined to crush the feudal nobility and seize its territories.

He was succeeded in 1495 by Manuel I, who was named "the Great" or "the Fortunate," because in his reign the sea route to India was discovered and a Portuguese Empire founded.

The Portuguese explorations were his main priority in government, pushing south the known coast of Africa with the purpose of discovering the maritime route to India and breaking into the spice trade.

During Sebastian's short personal reign, he strengthened ties with the Holy Roman Empire, England and France through diplomatic efforts.

Sebastian disappeared (and was presumably killed in action) in the battle of Alcácer Quibir in 1578, after the brief reign of King Henry triggering the Portuguese succession crisis.

Following the Portuguese crisis of succession, a dynastic union joined the crowns of Castile, Portugal and Aragon along with their respective colonial possessions, under the rule of the Habsburg dynasty The unification of the peninsula had long been a goal of the region's monarchs with the intent of restoring the Visigothic monarchy.

Portugal's long shoreline, with its many harbours and rivers flowing westward to the Atlantic Ocean was the ideal environment to raise generations of adventurous seamen.

The agriculture of the countryside had diversified to the point where grain was imported from Morocco (a symptom of an economy dependent upon Portugal's), while specialised crops occupied former grain-growing areas: vineyards, olives, or the sugar factories of the Algarve, later to be reproduced in Brazil (Braudel 1985).

The successive expeditions and experience of the pilots led to a fairly rapid evolution of Portuguese nautical science, creating an elite of astronomers, navigators, mathematicians and cartographers, among them stood Pedro Nunes with studies on how to determine the latitudes by the stars and João de Castro.

They are associated with the earliest discoveries, such as the Madeira Islands, the Azores, the Canaries, and to the early exploration of the north west African coast as far south as Arguim in the current Mauritania.

Due to the piracy that plagued the coasts, they began to be used in the navy and were provided with cannon windows, which led to the classification of "naus" according to the power of its artillery.

In India travels in the sixteenth century there were also used carracks, large merchant ships with a high edge and three masts with square sails, that reached 2000 tons.

The tables of the Almanach Perpetuum, by astronomer Abraham Zacuto, published in Leiria in 1496, were used along with its improved astrolabe, by Vasco da Gama and Pedro Álvares Cabral.

Besides coastal exploration, Portuguese also made trips off in the ocean to gather meteorological and oceanographic information (in these were discovered the archipelagos of Madeira and the Azores, and Sargasso Sea).

In 1517 King Manuel I of Portugal handed Lopo Homem a charter giving him the privilege to certify and amend all compass needles in vessels.

Prince Henry placed at the disposal of his captains the vast resources of the Order of Christ, of which he was the head, and the best information and most accurate instruments and maps that could be obtained.

He sought to effect a meeting with the half-fabulous Christian Empire of "Prester John" by way of the "Western Nile" (the Sénégal River), and, in alliance with that potentate, to crush the Turks and liberate the Holy Land.