With the advent of rotativismo and subsequent political stability, the attention of Portugal turned toward its colonial possessions in Africa. In East Africa, the chief settlement was Mozambique Island, but there was little control over the estates of the mainland where Portuguese of mixed ancesÍÍÍÍtry ruled as feudal potentates. In West Africa, the most important settlements were Luanda and Benguela on the Angolan coast, linked to Brazil by the slave trade conducted through the African island of São Tomé. It was during this period that the Portuguese began to send expeditions into the interior.

In 1852 António Francisco Silva Porto explored the interior of Angola. In 1877 a scientific expedition led by Hermenegildo Capelo and Roberto Ivens, two naval officers, and Alexandre Serpa Pinto, an army major, departed from Luanda and traveled to the Bié region in central Angola, where they separated. Serpa Pinto explored the headwaters of the Cuanza River in Angola and followed the course of the Zambezi River to Victoria Falls in present-day Zimbabwe. Exploring areas now part of South Africa, he crossed the Transvaal and arrived in Natal in 1879. In 1884 Capelo and Ivens departed from Moçamades on the coast of Angola and crossed the continent through entirely unexplored territory, arriving at Quelimane on the east coast of Mozambique in 1885. In the same year, Serpa Pinto and Augusto Cardoso explored the territory around Lake Nyassa. Various Portuguese, such as Paiva de Andrade and António Maria Cardoso, explored the interior of Mozambique.

Despite Portugal's historical claim to the Congo region, the colonial ambitions of the great powers of the day--Britain, France, and Germany--gave rise to disputes about its ownership. Portugal therefore proposed an international conference to resolve the disputed claim to the Congo. This conference, which met in Berlin in 1884-85, awarded the Congo to the king of Belgium and established the principle that in order for a claim to African territory to be valid, the claimant had to demonstrate "effective occupation," not historical rights. The Berlin Conference, as it is known, resulted in the partition of Africa among the European powers, and awarded Portugal Mozambique, Angola, and Guinea.

In 1886 Portugal signed two treaties that delimited the boundaries between Portuguese territories and those of France and Germany. France and Germany recognized Portugal's right to exercise sovereignty in the interior territory between Mozambique and Angola. This claim was represented on a map, annexed to the treaty with France, on which the claimed territory was colored red. In order to validate this claim, the Portuguese published the "rose-colored map" and organized successive expeditions into the interior between Mozambique and Angola. Meanwhile, the British were also exploring the territory from south to north under the auspices of Cecil Rhodes, who had designs on the territory for the construction of a railroad that would run from Cape Town through central Africa to Cairo.

Portugal protested against the activities of the British in what they con 3b6sidered d to be their territory. The British, having signed a number of treaties with African chiefs, claimed that the territory was under their protection and refused to recognize the rose-colored map. Moreover, they said the territory was not Portuguese because Portugal had not effectively occupied it as required by the terms of the Berlin Conference. Portugal proposed that the conflicting claims be resolved through arbitration. Britain refused and sent the Portuguese an ultimatum, on January 11, 1890, demanding the withdrawal of all Portuguese forces from the disputed territory. Portugal, faced with the armed might of the British, complied.

Data as of January 1993