The 1890 British Ultimatum was an ultimatum by the British government delivered on 11 January 1890 to Portugal in breach of the Treaty of Windsor of 1386. The ultimatum forced the retreat of Portuguese military forces in the land between the Portuguese colonies of Mozambique and Angola (most of present-day Zimbabwe and Zambia) which had been claimed by Portugal and included in its "Pink Map", which had clashed with British aspirations to create a Cape to Cairo Railway, thereby linking its colonies from the north of Africa to the very south.
When Portugal acquiesced to British demands, it was seen as a national humiliation by republicans in Portugal, who denounced the government and the King as responsible for it. The government fell, and António de Serpa Pimentel was appointed Prime Minister. The British Ultimatum inspired the original lyrics of the Portuguese National Anthem, "A Portuguesa". The 1890 British Ultimatum was considered by Portuguese historians and politicians at that time to be the most outrageous and infamous action of Britain against her oldest ally.[1]
On 20 August 1890 the Treaty of London was signed between Portugal and the United Kingdom, defining the territorial limits of Angola and Mozambique. The treaty was published in the Diário do Governo (Portugal's Government Diary) on 30 August and presented to the parliament that same day, leading to a new wave of protests and the downfall of the Portuguese government. When this treaty was not ratified, a new treaty was afterwards negotiated and accepted by both governments the following June. This ultimatum was one of the main causes for the Republican Revolution, which ended the monarchy in Portugal 20 years later.