The Iberian Peninsula, today home to Spain and Portugal, was overrun in the 5th century A.D. by the Visigoths, a Teutonic tribe from northern Europe and the conquerors of the Roman Empire. In 711, however, the Visigoths fell to the Moors, North African Muslims of mixed Berber-Arab heritage with roots in Mauritania. Their regime became one of the most culturally advanced in Europe. Religious toleration was established, but many of the indigenous people converted to Islam.
In succeeding centuries, Christian princes on the peninsula and neighboring co-religionists took up the cause of expelling the Moors from Europe (the Iberian Reconquista); for many the cause became a major pillar of their faith. This aim became coupled with an interest in exploration. Many Portuguese held a popular belief in the existence of Prester John, a semi-legendary Christian monarch, who was believed to be holding out against surrounding Muslim forces somewhere in Africa. It was hoped that explorations would locate the besieged forces, which would then join with Portuguese armies and expel the Moors from their lands.
As a small nation, Portugal may have appeared to be an unlikely leader in exploration and navigational science. Its geographical position, however, helped to shape its course. Surrounded to the east and north by Spain and having no outlets on the Mediterranean, Portugal was compelled to regard the Atlantic Ocean as its main medium of travel.
John I of Portugal (reigned 1385-1433) led his people into a period of high achievement and took direct aim at Moorish strength. The North African city of Ceuta (south across the Strait from Gibraltar) fell in 1415, giving a European power its first toehold on the African continent. Prince Henry (the Navigator), son of John and a hero at Ceuta, organized Portuguese resources and information for the purposes of exploration. Voyages were made into the Atlantic to the Madeira Islands and the Azores. Portugal emerged at the leading maritime power in Europe, but interest in exploration diminished after Henry's death in 1460.
John II (reigned 1481-95) revived overseas activity and employed two bold, innovative navigators:
Bartholomeu Dias headed a venture in 1487 that sought an all-water route to India; he was unable to complete his quest, but managed to round the southern tip of Africa and sail into the Indian Ocean.
Vasco da Gama extended Dias' journey in 1488, reached India and returned home with an alluring array of jewels and spices.
In 1494, two years after Columbus' first voyage, the pope attempted to divide newly discovered non-Christian lands between the two leading Catholic seafaring nations of the day. The Treaty of Tordesillas granted Spain possession of lands to the west of a prescribed line; Portugal was assigned lands to the east.
In 1500, Pedro Álvares Cabral was blown far off course, touched the coast of present-day Brazil and in doing so, established the Portuguese claim to that region.
Other Portuguese navigators pushed on to Cathay (China) and the Spice Islands (Indonesia), which established the beginnings of a Far Eastern empire. During a period in the early 16th century, Portugal became the most prosperous trading power and eclipsed the Italian city-states.
Portugal did not remain long at the top of the heap. As a small nation with severely limited internal resources, Portugal experienced chaos at home while its energies were focused abroad. Agriculture languished and industry failed to develop as it did elsewhere in Europe. A weakened Portugal soon fell under the influence of vastly superior Spain; the two nations were merged for 60 years in what was known as the Spanish Captivity (1580-1640). As Portugal declined, the upstart Dutch capitalized on the apparent weakness and seized many of the Portuguese possessions in the Far East.