From the Illustrated London News of 7 April 1900.
General Roberts (White) had recently turned the tide of the Boer War against Kruger (Black), with the recent relief of Ladysmith (28 February 1900) and capture of Bloemfontein (13 March).
But does the chess position in the advertisement make any sense?
The advertiser's confidence was a bit premature as a news report on page 2 of the same issue shows. The siege of Mafeking had not yet been lifted and the war continued for another two years.