The Second Boer war was what you are trying to find. The United Kingdom of Great Britain and Ireland fought against Southern African Republic in this war. The Orange Free State was also involved. The British war effort was supported by troops from several regions of the British Empire, including Southern Africa, the Australian colonies, Canada, Newfoundland, British India, and New Zealand. The war ended in victory for the British and the annexation of both republics. Both would eventually be incorporated into the Union of South Africa in 1910.