This study argues that the Zulu kingdom did not emerge as a revolutionary outburst; rather, that state formation among the northern Nguni-speaking peoples of Southern Africa began as much as a half-century before Shaka. The evidence suggests that this process began among lowland chiefdoms as a defensive response to the incursions of upland pastoralists. Lowland chiefdoms transformed traditional circumcision sets into multi-functional "amabutho" for better defence and productivity. When famine occurred in the early 1800s, major ruling houses made use of disciplined age-set regiments to compete for desirable ecological zones. The Zulu leader Shaka (c1787-1828) based his expansionary programme on these versatile "amabutho" and from them forged a centralized state.