describe Zulu fighting methods and tactics, including authors Ian Knight and Robert Edgerton. General histories of Southern Africa include Noel Mostert's "Frontiers" and a detailed account of the results from the Zulu expansion, J.D. Omer-Cooper's "The Zulu Aftermath", which advances the traditional Mfecane/Difaqane theory. The Mfecane History and legacy The increased military efficiency led to more and more clans being incorporated into Shaka's Zulu empire, while other tribes moved away to be out of range of Shaka's impis. The ripple effect caused by these mass migrations would become known (though only in the twentieth century) as the Mfecane/Difaqane (annihilation). Shaka's army set out on a massive programme of expansion, killing or enslaving those who resisted in the territories he conquered. His impis (warrior regiments) were rigorously disciplined: failure in battle meant death. At the time of his death, Shaka ruled over 250,000 people and could muster more than 50,000 warriors. His 10-year-long kingship resulted in a massive number of deaths, mostly due to the disruptions the Zulu caused in neighbouring tribes, although the exact death toll is a matter of scholarly dispute. Further unquantifiable deaths occurred during mass tribal migrations to escape his armies. The Mfecane produced Mzilikazi of the Khumalo, a general of Shaka's. He fled Shaka's employ, and in turn conquered an empire in Zimbabwe, after clashing with European groups like the Boers. The settling of Mzilikazi's people, the AmaNdebele or Matabele, in the south of Zimbabwe with the concomitant driving of the Mashona into the north caused a tribal conflict that still resonates today. Other notable figures to arise from the Mfecane/Difaqane include Soshangane, who expanded from the Zulu area into what is now Mozambique, and Zwangendaba. Disruptions of the Mfecane/Difaqane The theory of the Mfecane holds that the aggressive expansion of Shaka's armies caused a brutal chain reaction across the southern areas of the continent, as dispossessed tribe after tribe turned on their neighbours in a deadly cycle of fight and conquest. Some scholars contend that this theory must be treated with caution as it generally neglects several other factors such as the impact of European encroachment, slave trading and expansion in that area of Southern Africa around the same time. Normal estimates for the death toll range from 1 million to 2 million. These numbers are, however, controversial. According to Julian Cobbing, the development of the view that Shaka was the monster responsible for the