[2] He was promoted to major on 15 June 1885, served in the Egyptian Frontier Field Force from 1885 to 1886 and was Deputy Assistant Adjutant General in Cairo from 1885 to 1890.

Following his return to the United Kingdom, he was Brigade major of Royal Artillery, until in late 1899 he was reassigned following the outbreak of the Second Boer War.

[4] Following the end of the war, Lord Kitchener (Commander-in-Chief in South Africa) wrote in a despatch dated June 1902 how Sclater "possesses an unusual combination of ability and common sense.

[6] In recognition of services during the war, he was appointed a Companion of the Order of the Bath (CB) in the South Africa honours list published on 26 June 1902,[7] and he received the actual decoration from King Edward VII after his return, during an investiture at Buckingham Palace on 24 October 1902.

[8] In September 1902, Sclater accompanied Lord Roberts, Commander-in-Chief of the Forces, and St John Brodrick, Secretary of State for War, on a visit to Germany to attend the German army maneuvers as guest of the Emperor Wilhelm.