Britain's administration of Egypt and the Cape Colony contributed to a preoccupation over securing the source of the Nile River. Egypt was taken over by the British in 1882, leaving the Ottoman Empire in a nominal role until 1914, when London made it a protectorate. Egypt was never an actual British colony. Sudan, Nigeria, Kenya, and Uganda were subjugated in the 1890s and early 20th century; and in the south, the Cape Colony (first acquired in 1795) provided a base for the subjugation of neighbouring African states and the Dutch Afrikaner settlers who had left the Cape to avoid the British and then founded their own republics. Theophilus Shepstone annexed the South African Republic in 1877 for the British Empire, after it had been independent for twenty years. In 1879, after the Anglo-Zulu War, Britain consolidated its control of most of the territories of South Africa. The Boers protested, and in December 1880 they revolted, leading to the First Boer War. The Second Boer War, fought between 1899 and 1902, was about control of the gold and diamond industries; the independent Boer republics of the Orange Free State and the South African Republic were this time defeated and absorbed into the British Empire.

The Sudan was the key to the fulfillment of these ambitions, especially since Egypt was already under British control. This "red line" through Africa is made most famous by Cecil Rhodes. Along with Lord Milner, the British colonial minister in South Africa, Rhodes advocated such a "Cape to Cairo" empire, linking the Suez Canal to the mineral-rich South Africa by rail. Though hampered by German occupation of Tanganyika until the end of World War I, Rhodes successfully lobbied on behalf of such a sprawling African empire.