During the earlier part of the 19th century, many Afrikaner farmers left the eastern cape and moved inland. Among them was the Voortrekkers, a group of Afrikaners protesting British colonialism and seeking independent republics on what was reputedly empty land. But the land was not empty and clashes between these Afrikaners and indigenous peoples were inevitable.
Late in 1837 one of the Voortrekker leaders, Piet Retief, entered into negotiations for land with Dingane, the Zulu king. In terms of the negotiations Dingane promised the Voortrekkers land on condition they returned cattle to him stolen by Sekonyela (the Tlokwa chief). This Retief did and apparently he and Dingane signed a treaty on 6 February 1838. During the ceremony Dingane had Retief and his entourage murdered - an event which was witnessed by Francis Owen, a missionary who described the scene in his diary.
In ensuing battles between Zulus and Voortrekkers over the next few months numerous lives were lost on both sides.
On 16 December 1838 about 10 000 troops under the command of Dambuza (Nzobo) and Nhlela attacked the Voortrekkers, but the 470 Voortrekkers, with the advantage of gun powder, warded them off. Only three Voortrekkers were wounded, but more than 3 000 Zulus were killed during the battle.
In apartheid South Africa 16 December was known as Day of the Vow, as the Voortrekkers in preparation for the battle took a Vow before God that they would build a church and that they and their descendants would observe the day as a day of thanksgiving should they be granted victory. With the advent of democracy in South Africa 16 December retained its status as a public holiday, however, this time with the purpose of fostering reconciliation and national unity.