In 1899 Plumer returned to Southern Rhodesia where he raised a force of mounted infantry and, having been promoted to the substantive rank of lieutenant-colonel on 17 October 1900, he led them at the Relief of Mafeking during the Second Boer War. He was promoted to colonel on 29 November 1900 and was then given command of a mixed force which captured General Christiaan de Wet's wagon train at Hamelfontein in February 1901. Plumer arrived back in the United Kingdom in April 1902, and two months later was received in audience by King Edward VII on his return. In a despatch dated 23 June 1902, Lord Kitchener, Commander-in-Chief in South Africa during the latter part of the war, wrote how Plumer had "invariable displayed military qualifications of a very high order. Few officers have rendered better service."