Buller became head of the troops stationed at Aldershot in 1898. He was sent as commander of the Natal Field Force in 1899 on the outbreak of the Second Boer War. On seeing the list of troops which would make up his Corps Buller is said to have remarked "well, if I can't win with these, I ought to be kicked." By early September 1899 he had serious doubts that the Boers could not easily be browbeaten, and that White's forces in Natal might receive some punishment if they deployed too far forward. He arrived at the end of October. He was defeated at the Battle of Colenso, during what was later to become known as Black Week. Defeats at the Battle of Magersfontein and Battle of Stormberg also involved forces under his command. Because of concerns about his performance and negative reports from the field he was replaced in January 1900 as overall commander in South Africa by Lord Roberts. Defeats and questionable ability as commander soon earned him the nickname "Reverse Buller" among troops. He remained as second-in-command and suffered two more setbacks in his attempts to relieve Ladysmith at the battles of Spion Kop and Vaal Krantz. On his fourth attempt, Buller was victorious in the Battle of the Tugela Heights, lifting the siege on 28 February 1900, the day after Piet Cronje at last surrendered to Roberts at Paardeberg. After Roberts took Bloemfontein (13 March 1900), Buller correctly predicted that the Boers would take to guerrilla warfare. Later he was successful in flanking Boer armies out of positions at Biggarsberg, Laing's Nek and Lydenburg. It was Buller's veterans who won the Battle of Bergendal in the war's last set-piece action.