De Wet accompanied the expedition led by Gen. P. J. Liebenberg and Comm. Lucas Steenkamp, which set out by the end of January 1900. During February and March 1900, De Wet was active in organizing revolts in Prieska, Upington, and Kenhardt, and was promoted to commandant. The surrender of Gen.Piet Cronjé at Paardeberg on 27 February 1900, and the fall of Bloemfontein on 13 March 1900 obligated Republican forces to retreat quickly south of the Orange River. De Wet then helped defend the Orange Free State from British forces. He joined the Afrikaner Cavalry Corps when Comm. Abraham Malan founded it.
