In 1879 the Portuguese government formally claimed the area south and east of the Ruo River (which currently forms the southeastern border of
Malawi), and in 1882 occupied the lower
Shire River valley as far as the Ruo. The Portuguese then attempted to negotiate British acceptance of their territorial claims, but the convening of the
Berlin Conference (1884) ended these discussions. In 1884, Serpa Pinto was appointed as Portuguese consul in Zanzibar, and given the mission of exploring and re-mapping the region between
Lake Nyasa and the coast from the Zambezi to the
Rovuma River and securing the allegiance of the chiefs in that area. In 1885, Serpa Pinto undertook an expedition in 1885 with Lieutenant Augusto Cardoso as his second-in-command. Serpa Pinto fell seriously ill and was carried to the coast, where he eventually recovered. Cardoso his twenty-five-year-old lieutenant, continued the exploration, visiting Lake Nyasa and the
Shire Highlands, but failed to make any treaties of protection with the
Yao chiefs in territories west of the lake Malawi. Britain declined to accept the Portuguese claim that the Shire Highlands should be considered part of
Portuguese East Africa, as it was not under their effective occupation. In order to prevent Portuguese occupation, the British government sent
Henry Hamilton Johnston as British consul to Mozambique and the Interior, with instructions to report on the extent of Portuguese rule in the
Zambezi and Shire valleys and the vicinity, and to make conditional treaties with local rulers beyond Portuguese jurisdiction, to prevent them accepting protection from Portugal. In 1888, the Portuguese government instructed its representatives in Portuguese East Africa to attempt to make treaties of protection with the Yao chiefs southeast of Lake Malawi and in the Shire Highlands and an expedition organised under Antonio Cardoso, a former governor of
Quelimane, set off in November 1888 for the lake. Rather later, a second expedition led by Serpa Pinto, who had been appointed governor of Mozambique, moved up the Shire valley. Between them, these two expedition made over 20 treaties with chiefs in what is now Malawi. Serpa Pinto met Johnston in August 1889 east of the Ruo, when Johnston advised him not to cross the river into the Shire Highlands. Although Serpa Pinto had previously acted with caution, he crossed the Ruo to
Chiromo, now in Malawi in September 1889. Following minor clashes with Serpa Pinto's force, Johnston's deputy, John Buchanan, declared a British protectorate over the Shire Highlands, despite contrary instructions, although this was later endorsed by the
Foreign Office. ==Later life==