The Trekkers (only called Voortrekkers after 1880) were motivated by the fact that Zulu chief Dingane kaSenzangakhona had killed one of their leaders, Piet Retief, after negotiating a treaty with him. Dingane invited Piet Retief to his village and asked him and his men to leave their weapons at the gates. The Zulus then proceeded to butcher Retief and his men. Dingane's impis had also attacked Voortrekker encampments, killing an estimated 500 men, women, and children (including servants), most notably at Blaukraans. They even smashed the skulls of babies against the wheels of the trekker ox-wagon. The Trekker desire to succeed in settling in Natal was heightened by their isolation by the British administration of the Cape Colony. The British had effectively prevented supplies of ammunition and food from reaching the Trekkers overland, and had also blockaded the major Natal harbour.
The Trekkers asked Andries Pretorius to leave the Cape Colony and come to their aid against Dingane. Pretorius' subsequent election as military leader of a punitive commando on November 26, 1838 was the first of its kind in Boer history. Andries Pretorius was determined to seek revenge for the murder of Piet Retief and made a pact with God at Danskraal that was repeated by all the Voortrekkers each night . The Covenant held that a church would be built in his honour should they be victorious over the Zulu army.
Yet while Pretorius was in overall charge, other Boer leaders declined to submit completely to his authority . Consequently the commando was effectively divided into five sub-units. Unlike Piet Uys and Andries Potgieter earlier that year, Pretorius had the sense to avoid possible Zulu traps during his advance towards uMgungundlovu. The Zulu had defeated a punitive Trekker raid under Uys and Potgieter on February 6, 1838 at Italeni. One Zulu strategy was to lure Boers into rocky terrain to minimize the advantages a mounted rifleman had over a spear-carrying foot soldier. The superior numbers of the Zulu had to compensate for the technological advantages the Boers possessed.
On 15 December, after the Trekkers crossed the Buffalo River, one of their advance scouting parties brought warning of a large Zulu force that was approaching. While Cilliers wanted to ride out in attack, Pretorius declined, suspecting a trap. As site for the overnight camp, Pretorius chose an area next to the Ncome River, which provided a rear protection. The area provided no cover for an attacking force, and a deep dry riverbed protected one of the Trekker flanks. As usual, the ox wagons were drawn into a protective circle or laager. Movable wooden barriers that could be opened quickly were fastened between each wagon to prevent intruders, and two cannon were positioned.
During the night of the 15th, the Zulu, led by Dambuza (Nzobo) and Ndlela kaSompisi, started massing around the encampment. Mist settled over the site that evening. According to Afrikaner traditions, the Zulu were fearful to attack in the dark due to superstitions about the lamps which the Boers hung on whip-stocks around the laager Mackenzie suggests that the Zulu held back until what they perceived as the necessary numbers had arrived.
On 16 December, dawn broke on a clear day, revealing that " 'all of Zululand sat there' ," said one Trekker eyewitness. On his deathbed thirty years later, Sarel Cilliers recalled that before the battle commenced, the Trekkers had made a vow to God that if He should deliver them, they would build a church and commemorate the day as a Sabbath.
During the first phase of the attack, the Zulu repeatedly and unsuccessfully attacked the laager. The attackers were hindered by a change introduced during Shaka's rule, which replaced most of the longer throwing spears with short stabbing spears. The stabbing spear provided obvious advantages in close combat over its longer cousin. A Zulu eyewitness said that their first charge was mowed down like grass by the single-shot Boer muskets. Mackenzie claims that 200 indigenous servants looked after the horses and cattle and helped load muskets. Writing in the popular Afrikaans magazine, Die Huisgenoot, a Dr. D.J. Kotze said that this group comprised 59 "non-white" helpers and three English settlers with their black "followers."
After two hours and four waves of attack, Pretorius ordered a group of horsemen to leave the encampment and engage the Zulu in order to disintegrate their formations. The Zulu withstood the charge for some time, but rapid losses led them to scatter. The Boers pursued their fleeing enemies and hunted them down for three hours. Cilliers noted later that " 'we left the Kafirs lying on the ground as thick almost as pumpkins upon the field that has borne a plentiful crop.'
Bantjes recorded that about 3,000 dead Zulu had been counted, and three Trekkers were wounded. During the chase, Pretorius was wounded in his left hand by an assegaai (Zulu spear).
Four days after the battle, the victorious Vootrekkers arrived at Dingane's great kraal Mgungundlovu (near present day Eshowe) to find it deserted and ablaze. The bones of Retief and his men were found and buried where a memorial exists today.
Afterwards the clash was commemorated as having occurred at Blood River (Bloedrivier). 16 December is a public holiday in South Africa; before 1994 it was known as the Day of the Vow or Day of the Covenant; but today it is the Day of Reconciliation.
The conflict between the Zulu and Trekkers continued for almost two years afterwards. The idea of a decisive victory may have been planted in Pretorius' mind by a Zulu prisoner, who said that most of Dingane's warriors had either been killed or had fled. The same prisoner led some of the Trekker party into a trap at the White Umfolozi River, eleven days after the battle at Ncome River. This time the Zulu were victorious. Only when Dingane's brother, Mpande, defected to the Boer cause with a sizeable army, was Dingane finally defeated in January 1840.
Historian S.P. Mackenzie doubts the reported number of Zulu deaths. He compares Zulu casualties at Ncome to battles at Italeni, Isandhlwana, and Rorke's Drift. Mackenzie acknowledges that the casualty count was not impossible. Yet, in a similar victory on October 15, 1836 by Trekkers under Piet Retief over some 9,000 Matabele, the latter suffered only 350 casualties. In 1879 600 British soldiers with breech-loading rifles killed 2,000 Zulu over three hours before being overrun.
The official version not only represents the view of the winning side, but--like official accounts of the Great Trek and Anglo-Boer wars--leaves out the help provided by 200 indigenous people. Many Afrikaners were uneasy with the official version. Mackenzie notes that a Dutch Reformed clergymen later wrote that Blood River "'was not a battle, it was an execution.'"
A monument was erected on the site of the battle in 1947, consisting of an ox wagon executed in granite by the sculptor Coert Steynberg. In 1971 a laager of 64 ox wagons cast in bronze was erected, and unveiled on 16 December 1998.
At the 16 December 1998 inauguration of the most recent version of the monument, the Zulu politician and then Minister of Home Affairs, Mangosuthu Buthelezi, again apologized to the Afrikaner nation for the death of Piet Retief and the subsequent suffering. At the same time Buthelezi noted the suffering of the Zulu under the Afrikaner rule during apartheid. He stressed that South Africans needed to consider the day as "a new covenant which binds us to the shared commitment of building a new country.