The discovery of gold on the Witwatersrand in 1886 made the Transvaal, until then a struggling Boer republic, potentially a political and economic threat to British supremacy in South Africa at a time when Britain was engaged in the scramble for African colonies with France and Germany.
When the scheme of Cecil Rhodes, Prime Minister of the Cape Colony, to overthrow the Transvaal government of President Kruger by means of the so-called Jameson Raid, failed in 1896, Afrikaner nationalism again, like in 1877, flared up all over South Africa.
The Orange Free State concluded an alliance with the Transvaal. Although Paul Kruger was only interested in preserving the independence of the Transvaal, the British colonial secretary, Sir Joseph Chamberlain, and the British high commissioner in South Africa, Sir Alfred Milner, believed that the Transvaal was pressing for a united South Africa under the Afrikaaners.
Milner, a self-acknowledged race patriot, resolved that if the Transvaal would not reform, war would be the only way to eliminate a Boer oligarchy threatening British supremacy and to facilitate the development of the gold mining industry.
In order to become involved in the domestic issues of the Transvaal, he agitated that the foreign mineworkers (Uitlanders) should get the vote. In the diplomatic tussle that followed, Kruger refused to budge, despite a meeting with Milner in Bloemfontein in May – June 1899. A political deadlock was reached.
Britain rejected the Transvaal ultimatum which had demanded that all disputes between the two states be settled by arbitration; that British troops on the borders be withdrawn; and that troops bound for South Africa by ship should not disembark.
The Orange Free State joined the Transvaal in accordance with their alliance of 1897. On 11 October 1899, the second Boer War broke out.