Tension soon developed between the British Empire and the two Boer republics. The causes of the war were complex, with contributing factors including the Boers’ desire for independence (entailing harsh control of the Nguni and Sotho tribes in their territory), the prize of the rich gold fields, British colonial expansionist ambitions in Africa, perceived ill-treatment of British expatriates working in the Boer republics, the First Boer War and a failed uprising organised by Rhodes in the form of the Jameson Raid. Discussions broke down in October 1899 when the British ignored a Boer ultimatum to stop concentrating forces on the borders of the Boer republics.