Despite serious set @-@ backs at Colenso , Stormberg , Magersfontein , and Spion Kop in January — and with Ladysmith still under siege — the British mounted a five division counter @-@ invasion of the Orange Free State in February . The attacking force included a division of cavalry commanded by Lieutenant General John French with the New South Wales Lancers , Queensland Mounted Infantry and New South Wales Army Medical Corps attached . First , Kimberley was relieved following the battles of Modder River and Magersfontein , and the retreating Boers defeated at Paardeberg , with the New South Wales Mounted Rifles locating the Boer general , Piet Cronjé . The British entered Bloemfontein on 13 March 1900 , while Ladysmith was relieved . Disease began to take its toll and scores of men died . Still the advance continued , with the drive to Pretoria in May including more than 3 @,@ 000 Australians . Johannesburg fell on 30 May , and the Boers withdrew from Pretoria on 3 June . The New South Wales Mounted Rifles and Western Australians saw action again at Diamond Hill on 12 June . Mafeking was relieved on 17 May .