"Austral Africa: Losing It or Ruling It" is Mackenzie's account of events leading to the establishment of the protectorate. Influenced by Mackenzie, in January 1885 the British cabinet decided to send a military expedition to South Africa to assert British sovereignty over the contested territory. Sir Charles Warren (1840–1927) led a force of 4,000 imperial troops north from Cape Town. After making treaties with several African chiefs, Warren announced the establishment of the protectorate in March 1885. In September that year the Tswana country south of the Molopo River was proclaimed the Crown colony of British Bechuanaland. Mackenzie accompanied Warren, and "Austral Africa" contains a detailed account of the expedition.