In Natal, on 6 February 1838, Piet Retief, Voortrekker Leader, and his party of 69 men were unexpectedly butchered to death while feasting with the Zulus. They were celebrating the signing of a treaty ceding land to the Voortrekkers. The Battle of Blood River on 16 December 1838 was to avenge their death.

There were several more attacks on the Voortrekkers after Retief's murder at mGgundgundlovu (Dingaan, the Zulu chief's capital). There was one at Weenen, Bloukrans and Moordplaas (Murder Farm). Hundreds of men, women and children were killed. The Voortrekkers and British launched a number of punitive expeditions against the Zulus, but these were all inconclusive.

The Voortrekkers became very despondent. Then a charismatic man from Graaff Reinet, called Andries Pretorius, appeared on the scene and took over the leadership. Soon plans were finalised for a decisive attack on Dingaan.

Andries Pretorius' commando, later known as the Winkommando ("Victorious commando') was made up of some 470 men. They crossed the Buffalo River (near present-day Dundee) and reached a tributary on Saturday 15 December 1838. The tributary has since been known as the Blood River.

Scouts reported seeing a large Zulu impi of about 12 500 men advancing. Pretorius carefully selected the best strategic position to form his laager: between a deep pool in the river and a donga, which joined the river on the opposite side. The wagons were securely tied together, gates were provided and cannons were placed in the only two openings.

The Zulus fought with shields and assegaais. To be able to use their assegaais effectively they had to get as close as possible to the enemy. The Voortrekkers had far superior weapons; muzzle-loaders, flint-lock muskets and cannons. At dusk, the Zulu impis were clearly visible, massed on the opposite bank of the river.

Two hours before dawn everybody was ready. The Voortrekkers once more recited the Covenant and made their vow with God; that if God granted the Voortrekkers victory, they would for ever observe the day as a Sabbath and build a church as a memorial for future generations.

The assault came at dawn the following day. The dense fog that covered the ground completely cleared at daybreak. The first attack was repulsed successfully. The second one could not be beaten back until it had almost reached the wagons. When the Zulus, who had again withdrawn to about 500 yd, hesitated to launch a third attack, Pretorius sent some men to draw them out.

The final attack lasted almost an hour. When the force of the attack began to weaken, Pretorius sent out a few hundred horsemen. Finally, the Zulus were put to flight and the Winkommando pursued them for hours.

Towards midday, when the pursuit was called off, more than 3 000 corpses was counted around the laager. The water in the river had turned red with blood. Only three Voortrekkers were wounded, including Pretorius himself, and none were killed.A solemn thanksgiving service was held.

The memorial church was built in Pietermaritsburg two years later. Two monuments on the site commemorate the battle. The first is an ox-wagon sculptured out of grey granite by Coert Steynberg. Nearby is the laager reconstructed as on that day with 57 full-size replicas of ox-wagons cast in bronze. Since 1995 the name of the holiday on 16 December has been changed from the Day of the Covenant to the Day of Reconciliation.

Blood River is regarded as one of the great battles ever fought in South Africa.