In the wake of the Reconquista, Portuguese sailors began exploring the coast of Africa and the Atlantic archipelagos in 1418–1419, using recent developments in navigation, cartography, and maritime technology such as the caravel, with the aim of finding a sea route to the source of the lucrative spice trade.

[5] After establishing itself as a separate kingdom in 1139, Portugal completed its reconquest of Moorish territory by reaching Algarve in 1249, but its independence continued to be threatened by neighbouring Castile until the signing of the Treaty of Ayllón in 1411.

[6] Free from threats to its existence and unchallenged by the wars fought by other European states, Portuguese attention turned overseas and towards a military expedition to the Muslim lands of North Africa.

It offered the opportunity to continue the Christian crusade against Islam; to the military class, it promised glory on the battlefield and the spoils of war;[8] and finally, it was also a chance to expand Portuguese trade and to address Portugal's economic decline.

[11] A key supporter of this policy was Infante Dom Henry the Navigator, who had been involved in the capture of Ceuta, and who took the lead role in promoting and financing Portuguese maritime exploration until his death in 1460.

[20] The first feitoria trade post overseas was established in 1445 on the island of Arguin, off the coast of Mauritania, to attract Muslim traders and monopolise the business in the routes travelled in North Africa.

[24] In 1469, after prince Henry's death and as a result of meagre returns of the African explorations, King Afonso V granted the monopoly of trade in part of the Gulf of Guinea to merchant Fernão Gomes.

[33] These were eventually settled by the Treaty of Tordesillas in 1494, which divided the world outside of Europe in an exclusive duopoly between the Portuguese and the Spanish along a north–south meridian 370 leagues, or 970 miles (1,560 km), west of the Cape Verde islands.

[38] The squadron of Vasco da Gama left Portugal in 1497, rounded the Cape and continued along the coast of East Africa, where a local pilot was brought on board who guided them across the Indian Ocean, reaching Calicut, the capital of the kingdom ruled by Zamorins, also known as Kozhikode) in south-western India in May 1498.

The land was found to be abundant in pau-brasil, or brazilwood, from which it later inherited its name, but the failure to find gold or silver meant that for the time being Portuguese efforts were concentrated on India.

[41] In 1502, to enforce its trade monopoly over a wide area of the Indian Ocean, the Portuguese Empire created the cartaz licensing system, granting merchant ships protection against pirates and rival states.

That year the Portuguese also conquered Kannur, where they founded St. Angelo Fort, and Lourenço de Almeida arrived in Ceylon (modern Sri Lanka), where he discovered the source of cinnamon.

[45] In the same year, Manuel I ordered Almeida to fortify the Portuguese fortresses in Kerala and within eastern Africa, as well as probe into the prospects of building forts in Sri Lanka and Malacca in response to growing hostilities with Muslims within those regions and threats from the Mamluk sultan.

[49] Although requested by Manuel I to further explore interests in Malacca and Sri Lanka, Almeida instead focused on western India, in particular the Sultanate of Gujarat due to his suspicions of traders from the region possessing more power.

[57] He encouraged Portuguese settlers to marry local women, built a church in honor of St. Catherine (as it was recaptured on her feast day), and attempted to build rapport with the Hindus by protecting their temples and reducing their tax requirements.

[74][75] In 1514, Afonso de Albuquerque, the viceroy of the Estado da India, dispatched Rafael Perestrello to sail to China in order to pioneer European trade relations with the nation.

[106] In east-Africa, the main agents acting on behalf of the Portuguese Crown, exploring and settling the territory of what would become Mozambique were the prazeiros, to whom vast estates around the Zambezi River were leased by the King as a reward for their services.

Commanding vast armies of chikunda warrior-slaves, these men acted as feudal-like lords, either levying tax from local chieftains, defending them and their estates from marauding tribes, participating in the ivory or slave trade, and becoming involved in the politics of the Kingdom of Mutapa, to the point of installing client kings upon its throne.

[112] Based on the Treaty of Tordesillas, the Portuguese Crown, under the kings Manuel I, João III and Sebastão, also claimed territorial rights in North America (reached by John Cabot in 1497 and 1498).

In 1503, an expedition under the command of Gonçalo Coelho reported French raids on the Brazilian coasts,[115] and explorer Binot Paulmier de Gonneville traded for brazilwood after making contact in southern Brazil a year later.

[118] In 1531, a royal expedition led by Martim Afonso de Sousa and his brother Pero Lopes went to patrol the whole Brazilian coast, banish the French, and create some of the first colonial towns – among them São Vicente, in 1532.

In 1583, merchant and explorer Jan Huyghen van Linschoten (1563 – 8 February 1611), formerly the Dutch secretary of the Archbishop of Goa, had acquired information while serving in that position that contained the location of secret Portuguese trade routes throughout Asia, including those to the East Indies and Japan.

The Dutch attained victories in Asia and Africa with assistance of various indigenous allies, eventually wrenching control of Malacca (1641), Portuguese Gold Coast (1642), Ceylon (1658), and Kochi (1663).

Although he failed to spike the gold revenue, two short-term companies he established for the plantation economy drove a significant increase in production of cotton, rice, cacao, tobacco, and sugar.

The existence of the remaining Portuguese colonies in India became increasingly untenable and Nehru enjoyed the support of almost all the Indian domestic political parties as well as the Soviet Union and its allies.

In 1961, shortly after an uprising against the Portuguese in Angola, Nehru ordered the Indian Army into Goa, Daman and Diu, which were quickly captured and formally annexed the following year.

The same year, the tiny Portuguese fort of São João Baptista de Ajudá in Ouidah, a remnant of the West African slave trade, was annexed by the new government of Dahomey (now Benin) that had gained its independence from France.

[211] According to one historian, Portuguese rulers were unwilling to meet the demands of their colonial subjects (unlike other European powers) in part because Portuguese elites believed that "Portugal lacked the means to conduct a successful "exit strategy" (akin to the "neocolonial" approach followed by the British, the French, or the Belgians)" and in part due to the lack of "a free and open debate [in Salazar's dictatorial state] on the costs of upholding an empire against the anti-colonial consensus that had prevailed in the United Nations since the early 1960s".

[212] The rise of Soviet influence among the Movimento das Forças Armadas's military (MFA) and working class, and the cost and unpopularity of the Portuguese Colonial War (1961–1974), in which Portugal resisted to the emerging nationalist guerrilla movements in some of its African territories, eventually led to the collapse of the Estado Novo regime in 1974.

[216] In 1987, Portugal signed the Sino-Portuguese Joint Declaration with the People's Republic of China to establish the process and conditions for the transfer of sovereignty of Macau, its last remaining overseas possession.