The essence of the military campaign in Natal was the siege and relief of Ladysmith. At the outbreak of war the colony was invaded by commandos of the Orange Free State, pouring in through the Tintwa, Van Reenen and Bezuidenhout passes, and the Transvaal forces of General Joubert, who by the end of October 1899 had captured Charlestown, Newcastle and Dundee. Between 29 October and 2 November Joubert laid siege to Ladysmith, where the British and colonial forces from the frontier region had retired. Although advanced Boer patrols reached Mooiriver, only fifty miles from Pietermaritzburg, Joubert's commandos concentrated around Ladysmith rather than advance in force towards Durban and the sea. Three attempts by General Buller to relieve Ladysmith ended in defeats at Colenso (15 December), Spion Kop (24 January) and Vaalkrans (5–7 February). After four months the town was eventually relieved on 28 February. Thereafter the Boer forces were pushed back to the colony's frontiers. Dundee was entered by imperial troops on 16 May and Newcastle two days later, and by the end of May the whole of Natal and Zululand was once again under British control.

Events in Natal are especially interesting from the point of view of black involvement in the war. In the first place Natal was the settler colony in South Africa in which the proportion of colonists to black people was smallest; whites were outnumbered 10:1 in Natal. Secondly, the colony was the scene of some of the most intense fighting in the war.