[Gaza] kingdom established in the highlands of the middle Sabi River in Mozambique in the 1830s by Soshangane, the Ndwandwe general who fled from Zululand after his defeat at the hands of Shaka during the Zulu-Nguni wars known as the Mfecane. Soshangane extended his control over the area between the Komati (Incomati) and the Zambezi rivers, incorporating the local Tsonga and Shona peoples into his Zulu-type state and reducing the Portuguese to tributary status. 

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Initially, Shaka's most formidable rivals were the Ndwandwe, under the leadership of Zwide, who had driven Matiwane's Ngwane people onto the Highveld and Sobhuza's Ngwane north across the Pongola river, beyond the Zulu orbit. There, Sobhuza established the new conquest state of Swaziland (named for his successor, Mswati). In 1820 and again in 1823 Shaka defeated Zwide's armies, which broke into several groups. Zwide himself retired, but his generals fled northward... the Ndwandwe general Soshangane established the extensive Gaza kingdom in south-central Mozambique. At its height, the Gaza kingdom stretched between the Zambezi and the Komati rivers; Soshangane engaged in slave trading with the Portuguese and reduced neighbouring Shona to tributary status. Adding greatly to the social dislocation of east-central Africa, Ngoni movements were dictated by the need to avoid more powerful African polities and to find new food resources after local cattle and crops had been exhausted through their raids. Within their military states, the Ngoni aristocracy monopolized cattle, incorporated the women and children of conquered peoples, and exacted tribute from those whom they were unable to permanently subdue.