From The Penguin History Of Latin America, by Edwin Williamson (Penguin, 2003), Kindle pp. 70-72:
Portugal’s experience of the Reconquest and her Iberian cultural heritage made her share many characteristics with her neighbour Castile, their cognate histories frequently crossing and overlapping with each other. As in the case of Castile, the centuries of fighting against the Muslims produced a society in which religion had a crusading quality and was closely associated with the national identity. The system of land tenure was similar to Castile’s: in the fertile, well-populated north, there were a large number of smallholders and tenant farmers; in the south the latifundium and a seigneurial regime predominated.
The Portuguese were not particularly given to seafaring. Though fishing was significant, most of the population were actually peasants who worked the land. Still, Portuguese society was motivated by aristocratic and military values, and, with its reconquest concluded some two centuries before Castile’s, Portugal’s quest for glory and riches was carried abroad to North Africa and into the Atlantic, where the spirit of adventure of a small minority was to lead to remarkable feats of maritime exploration and empire-building. Exploits overseas, however, went hand in hand with commerce, stimulated by the presence of considerable numbers of Genoese merchants and mariners who had settled along the coast, and especially in Lisbon, which was by far the most populous city.
The Portuguese monarchy in the thirteenth and fourteenth centuries was constantly under threat from ambitious nobles, from a powerful Church, and, not least, from dynastic quarrels in which the hand of Castile was invariably suspected, and with good reason. Relations with Spain would remain ambivalent: the larger neighbour exerted a very powerful influence on culture as well as politics, but there would always exist forces of repulsion, and Portuguese foreign policy was chiefly concerned with maintaining national independence from Castile. Portugal’s long association with England – starting as a trading relationship in the twelfth century and periodically formalized by a series of treaties – stemmed from the need for a strong ally to counterbalance the perennial threat of incorporation by Spain.
A turning-point came in 1385 at the battle of Aljubarrota, when a new king, John of Aviz, nominated by the Portuguese Cortes and aided by English allies, won a victory against Castile and the Portuguese nobles. The long reign of John I (1385–1433) saw the development of a powerful monarchy capable of creating a stable nation state largely free from baronial challenges and galvanized by a renewal of the crusading spirit, though this was now directed towards Africa: the imperial phase of Portuguese history began with the taking of Ceuta in 1415. A few years later, John’s son, Prince Henry the Navigator, established a school of navigation at Sagres on the Algarve and became the patron of the voyages of exploration that would continue long after his death in 1460 and would eventually open Africa, India and the East to the Europeans.
The death of John I was followed by an interlude of aristocratic revolt and dynastic civil wars, the latter overlapping with the wars of succession which put Isabella on the Castilian throne. In Portugal, John II (1481–95) finally imposed order and proceeded, by a combination of murders and executions, to break the power of the nobility and confiscate much of its wealth. It was John II who finally created in Portugal an absolutist nation state resembling the Catholic monarchy of Spain, with the Church playing a crucial role in giving a monopoly of legitimacy to the unifying authority of the Crown.
For eighty years after John’s death, Portugal’s Catholic monarchy supervised the building of one of the most far-flung empires ever to have been created by Europeans: in 1487 the Cape of Good Hope was rounded by Bartholomew Dias; by 1498 Vasco da Gama had reached India; the year 1500 saw another Portuguese expedition discover a land that would eventually become Brazil; in the course of the sixteenth century the Portuguese established bases and factories in Ceylon, Malacca and the Spice Islands of the Indonesian archipelago; by the 1570s they had won a monopoly of the lucrative trade between China and Japan from a base established at Macao on the Chinese mainland in 1557.