The Second Boer War was fought from 11 October 1899 to 31 May 1902, between the British Empire and the two independent Boer republics of the Orange Free State and the South African Republic (Transvaal Republic). After a set of failed negotiations over foreigner land rights in the territories, led by Joseph Chamberlain, both sides issued ultimatums. When the ultimatums were rejected, war was declared. The war had three distinct phases. First, the Boers mounted pre-emptive strikes into British-held territory in Natal and the Cape Colony, besieging the British garrisons of Ladysmith, Mafeking and Kimberley. The Boers then won a series of tactical victories against a failed British counteroffensive to relieve the three sieges. The second phase began after British forces under Frederick Roberts, 1st Earl Roberts launched counteroffensives with increased troop numbers. After Natal and the Cape Colony were secure, the British were able to invade the Transvaal and the republic's capital, Pretoria, was captured in June 1900. The third phase began in March 1900, when the Boers engaged a protracted hard-fought guerrilla warfare against the British forces. In an effort to cut off supplies to the raiders, the British, now under the leadership of Lord Kitchener, responded with a scorched earth policy of destroying Boer farms and moving civilians into concentration camps.