1890 British Ultimatum

[2] At the start of the 19th century, the Portuguese presence in Africa south of the equator was limited in Angola to Luanda and Benguela and a few outposts, the most northerly of which was Ambriz and in Mozambique to the Island of Mozambique, several other coastal trading posts as far south as Delagoa Bay and the virtually independent Prazo estates in the Zambezi valley [3] The first challenge to Portugal's wider claims came from the Transvaal Republic, which in 1868 claimed an outlet to the Indian Ocean at Delagoa Bay.

Portugal occupied the coast of Mozambique from the 16th century, and from 1853 the Portuguese government embarked on a series of military campaigns to bring the Zambezi valley under its effective control.

[9] To validate Portuguese claims, Serpa Pinto was appointed as its consul in Zanzibar in 1884 and given the mission of exploring 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.

[12] Despite the outcome of the Berlin Conference, the idea of a trans-African Portuguese zone was not abandoned; to help to create it, Portugal signed treaties with France and Germany in 1886.

Following the treaties, the Portuguese foreign minister prepared what became known as the Rose Coloured Map, representing a claim stretching from the Atlantic to the Indian Ocean.

[14] In 1888, the Portuguese government instructed its representatives in Mozambique to make treaties of protection with the Yao chiefs southeast of Lake Nyasa and in the Shire Highlands.

[22] What Her Majesty's Government require and insist upon is the following: that telegraphic instructions shall be sent to the governor of Mozambique at once to the effect that all and any Portuguese military forces which are actually on the Shire or in the Makololo or in the Mashona territory are to be withdrawn.

Mr. Petre is compelled by his instruction to leave Lisbon at once with all the members of his legation unless a satisfactory answer to this foregoing intimation is received by him in, the course of this evening, and Her Majesty's ship Enchantress is now at Vigo waiting for his orders.

[23] Although the ultimatum required Portugal to cease from its activities in the disputed areas, there was no similar restriction on further British efforts to establish occupation there.

Agents for Rhodes were active in Mashonaland and Manicaland and in what is now eastern Zambia, and John Buchanan asserted British rule in more of the Shire Highlands.

[26] In an attempt to reach an agreement over Portuguese African borders, the Treaty of London defining the territorial limits of Angola and Mozambique, was signed on 20 August 1890 by Portugal and the United Kingdom.

[27] The 1890 ultimatum soured Anglo-Portuguese relations for some time, although when in the late 1890s Portugal underwent a severe economic crisis, its government sought a British loan.

In return, Portugal agreed to stop arms being supplied to the Transvaal through Lourenço Marques and declared its neutrality in the conflict.