Lieutenant Robert Wilfred Sharpe joined the Imperial Yeomanry Scouts in March 1900 and was taken prisoner at Roodeval on 7.6.1900, when de Wet captured and destroyed the Rhenoster River bridge. The garrisons of Roodewal, Rhenoster River and Vredefort Road Station were surrounded and overwhelmed in a dawn attack. Casualties ran into hundreds and most damaging for Roberts' force was the loss of over 100,000 worth of supplies. De Wet also burnt all the mail.

The Imperial Yeomanry Scouts were disbanded in December 1900 and Sharpe was commissioned into the Prince of Wales's Light Horse on 4.1.1901, when this unit was raised at Cape Town. The Prince of Wales's Light Horse, known as the "South African Welsh", served in Colonel Bethune's Column and took part in many skirmishes in the Orange Free State and Cape Colony. It was disbanded in December 1901 and the majority of men paid off. A handful remained on strength until early 1902 and 18 were entitled to the King's South Africa Medal. Sharpe was one of these (not all the Medals were issued) and resigned in March 1902.

He subsequently served in the Bambata Rebellion with the Northern District Mounted Rifles, raised in Natal in 1902, and was one of the 'Warrant And Non-Commissioned Officers and Men Who Were Brought To Notice For Good Service' (The Zulu Rebellion of 1906 refers). Sharpe was commissioned, promoted Lieutenant in 1907 and was Adjutant when the Northern District Mounted Rifles were disbanded on the formation of the Union Defence Force in 1913.