While events were unfolding at the Cape, the slave trade at Delagoa Bay had been expanding since about 1810 in response to demands for labor from plantations in Brazil and on the Mascarene Islands. During the late 1820s, slave exports from the Delagoa Bay area reached several thousand a year, in advance of what proved to be an ineffective attempt to abolish the Brazilian trade in 1830. After a dip in the early 1830s, the Bay slave trade peaked in the late 1840s.

The impact of the slave trade was increasing destabilization of hinterland societies as populations were forcibly removed. The Gaza, Ngoni, and other groups became surrogate slavers and joined the Portuguese soldiers in inland raiding. Along the Limpopo and Vaal river networks, Delagoa Bay slavers competed with Griqua slavers in supplying the Cape. After slavers burned crops and famines became common, many groups—including the Ngwane, Ndebele, and some Hlubi—fled westward into the Highveld mountains during the 1810s and ’20s. The Kololo, on the other hand, moved east out of Transorangia, where they ran into Bay slavers, and migrated west into Botswana. In 1826 they were attacked by an alliance of Ngwaketse and European mercenaries and ended up in Zambia in the 1850s exporting slaves themselves to the Arabs and Portuguese.

Emergence of the eastern states

Four main defensive African state clusters had emerged in eastern South Africa by the 1820s: the Pedi (led by Sekwati) in the Steelpoort valley, the Ngwane (led by Sobhuza) in the eastern Transvaal, the Mokoteli (led by Moshoeshoe) in the Caledon River region, and the Zulu (led by Shaka) south of the Swart-Mfolozi River. The Pedi received refugees from the Limpopo and coastal plains, and the Mokoteli absorbed eastern Transorangian refugees, which enabled them to defeat the Griqua and Korana raiders by the mid-1830s. By 1825 Shaka had welded the Chunu, Mthethwa, Qwabe, Mkhize, Cele, and other groups into a large militarized state with fortified settlements called amakhanda. Zulu amabutho (age sets or regiments) defended against raiders, provided protection for refugees, and, apparently, began to trade in ivory and slaves themselves.

From 1824 the Zulu began to clash with Cape colonists who came to Port Natal (renamed Durban in 1835) and organized mercenary armies. These groups were comparable to the Portuguese prazero armies along the Zambezi and to the warlord state set up by the Portuguese trader João Albasini in the eastern Transvaal in the 1840s, but they operated on a smaller scale. During the 1820s European raiders joined Zulu amabutho in attacking areas north of the Swart-Mfolozi River and south of the Mzimkulu River, where in the mid-1820s French ships exported slaves. Francis Farewell’s raiders, in alliance with Zulu groups, seized women and children in the same area in 1828.

Conflicts split the Zulu elite into rival factions and led to Shaka’s assassination in 1828. Shaka’s half brother Dingane became the Zulu leader, but his succession was accompanied by civil wars and by increasing interference in the Delagoa Bay trading alliances. By the mid-1830s a coalition of Cape merchants had begun planning for the formal colonization of Natal, with its superb agricultural soils and temperate climate. The British left the less-desirable malaria-ridden Delagoa Bay region to the Portuguese, who traded slaves out of Lourenço Marques (now Maputo, Mozambique) for another half century.

The Great Trek

A few Boer settlers had moved north of the Orange River before 1834, but after that the number increased significantly, a migration later known as the Great Trek. The common view that this was a bid to escape the policies of the British—i.e., the freeing of slaves—is difficult to sustain, as most of the former slave owners did not migrate (most trekkers came from the poorer east Cape), and the earlier labor shortage had been alleviated by 1835. Instead, the trek was more of an explosive culmination of a long sequence of colonial labor raids, land seizures, punitive commando raids, and commercial expansions. Europeans, who possessed technologically advanced weaponry, also had instructive examples of how small groups of raiders in Natal and Transorangia could cause disruption over large areas. Thus, the trekkers should not be seen as backward feudalists escaping the modern world, as some historians have maintained, but as energized people extending their frontier.

Several thousand Boers migrated with their families, livestock, retainers, wagons, and firearms into a region already destabilized and partially depopulated by Griqua and coastal raiders. They did encounter some Africans (such as the Ndebele), who in the early 1830s had moved from the southeastern to the western Transvaal. The Boers and their Rolong, Taung, and Griqua allies, however, crushed the Ndebele during 1837, taking their land and many cattle, women, and children. The remaining Ndebele fled north, where they resettled in southern Zimbabwe.

The trekkers had penetrated much of the Transvaal by the early 1840s. A grouping of commando states emerged based at Potchefstroom, Pretoria, and, from 1845, Ohrigstad-Lydenburg in the eastern Transvaal. Andries Hendrik Potgieter, Andries Pretorius, Jan Mocke, and others competed for followers, attacked weaker African chiefdoms, hunted elephants and slaves, and forged trading links with the Portuguese. Other Boers turned east into Natal and allied themselves with the resident British settlers. Farms developed slowly and, as had been the case in the Cape prior to the 1830s, depended on forced labor. Until the 1860s the Pedi and Swazi in the east and even the Kwena and Hurutshe in the west were strong enough to avoid being conscripted as labor and thus limited the labor supply.

The British in Natal

The appearance of thousands of British settlers in Natal in the 1840s and ’50s meant that for the first time Africans and European settlers lived together—however uneasily—on the same land. The Boers began to carve out farms in Natal as they had done along the eastern frontier, but further slave and cattle raids on the Bhaca south of the Mzimkulu provided the pretext for British annexation of Natal in 1843. Theophilus Shepstone received an appointment in 1845 as a diplomatic agent (later secretary for native affairs), and his position served as a prototype for later native commissioners. The Harding Commission (1852) set aside reserves for Africans, and missionaries and pliant chiefs were brought in to persuade Africans to work. After 1849 Africans became subject to a hut tax intended to raise revenue and drive them into labor. Roads were built, using forced labor, and Africans were obliged to pay rent on state land and European farms. To meet these burdens some African cultivators grew surplus crops to sell to the growing towns of Pietermaritzburg and Durban.

The British were reluctant, though, to annex the Transorangian interior, where no strategic interests existed. Boer trade links with Delagoa Bay posed little threat because Portugal was virtually a client state of Britain. To the Boers fell the tasks of eroding African resistance and developing the land, although the policy never received clear enunciation or much financial backing. Britain halfheartedly attempted to protect some of its African client states, such as that of the Griqua and the Sotho state led by Moshoeshoe. However, after further fighting with the Rharhabe-Xhosa on the eastern frontier in 1846, Governor Colonel Harry Smith finally annexed, over the next two years, not only the region between the Great Fish and the Great Kei rivers (establishing British Kaffraria) but also a large area between the Orange and Vaal rivers, thus establishing the Orange River Sovereignty. These moves provoked further warfare in 1851–53 with the Xhosa (joined once more by many Khoe), with a few British politicians ineffectively trying to influence events.

A striking feature of this period was the capacity of the Sotho people to fend off military conquest by the British and Boers. After defeating and absorbing the rival Tlokwa in 1853–54, Moshoeshoe became the most powerful African leader south of the Vaal-Pongolo rivers. His soldiers utilized firearms and, in the cold Highveld, horses—which proved to be the keys to political and military survival there.