The Butua state was one of the largest pre-colonial state systems, established in southern Africa in the early 15th century. The state was initially centered at Khami but the capital moved to Danamombe in the 17th century. A defining characteristic of the Butua state was its architecture, which is predominantly made up of terraced platforms built using the technology of dry-stone masonry. The state covered a large area that includes modern-day southern and south-western parts of Zimbabwe, north-east Botswana, and northern South Africa. The Butua state thrived on a number of key economic activities that included mining of various minerals, including gold, which was in high demand from Portuguese and Swahili traders on the Indian Ocean coast. Various metals were also processed to provide a range of utilitarian or ornamental objects made of gold, copper, iron, or alloys of more than one metal. Other economic pillars of the Butua state included cattle farming, agriculture, and local exchange of commodities as well as participation in global exchange networks through the Indian Ocean.
States that flourished in the area immediately south of the Zambesi River from the 15th to the 19th centuries were ruled by Karanga dynasties and were the cultural heirs of Great Zimbabwe. The most important of these states was Mokaranga, whose rulers bore the title of Monomotapa. Other important states—Teve, Manica, Barue, and Butua—all depended on the mining and trading of gold. Commerce was conducted at fairs attended by merchants from coastal towns such as Sofala and Chibuene, which were part of the networks of Indian Ocean commerce. At the beginning of the 16th century this trade attracted Portuguese traders who visited the fairs. In the 17th century, the Portuguese gradually expanded their presence through the institution of the prazos, whose owners acquired jurisdiction over extensive areas formerly ruled by the Karanga. The Portuguese were expelled from the Zimbabwe plateau in the 1690s and were succeeded by the Rosvi, another Karanga ruling elite. These states were devastated by droughts from the 1790s to the 1830s. All of them experienced civil wars before they were conquered by the Ngoni, who established the kingdom of Gaza, which covered the whole area south of the Zambesi as far as the Limpopo River until the time of the Scramble for Africa. Some of the old Karanga states, notably Manica and Barue, survived as tributaries of the Gaza state.