He is widely credited with uniting many of the Northern Nguni people, specifically the Mtetwa Paramountcy and the Ndwandwe into the Zulu Kingdom, the beginnings of a nation that held sway over the portion of southern Africa between the Phongolo and Mzimkhulu Rivers, and his statesmanship and vigour marked him as one of the greatest Zulu kings.[3] He has been called a military genius for his reforms and innovations, and condemned for the brutality of his reign.[4][5] Other historians debate about Shaka's role as a uniter, versus a usurper of traditional Zulu ruling prerogatives, and the notion of the Zulu state as a unique construction, divorced from the localised culture and the previous systems built by his predecessor Dingiswayo.[6] Research continues into the character and methods of the Zulu warrior king, whose reign still greatly influences South African culture.