The era between the early second millennium and circa 1600 is significant as adiscrete unit of study owing to several key developments. The era of the greatcavalry empires in the western and central savannah reached its apex in Mali andSonghay, but by the beginning of the seventeenth century, alternative frameworksfor military activity would emerge, moving away from the empire-state modelwhich had dominated the region for so long. Another military state with itsroots in antiquity, Solomonic Ethiopia, would likewise achieve remarkablesuccess in the fourteenth and fifteenth centuries, before a series of wars inthe sixteenth brought it to the point of extinction. Unlike its West Africancounterparts, however, Ethiopia would survive – just. Further south, thefoundations built in the first millennium, particularly in the wake of the Bantudiffusion and attendant political and economic transformation, would be used tocreate some of the most dynamic military organisations on the continent by theend of the sixteenth century, if frequently more compact and less concerned withthe overt control of territory than some of their counterparts north of theforest zone. A series of state and non-state structures emerged acrosssub-Saharan Africa, each in different ways placing war at the centre of policyand culture. Some of these would prove remarkably durable. Once again, as inearlier centuries, migratory movements proved seminal. If the Bantu expansionand Arab migrations had been among the crucial dynamics of antiquity, in thefirst half of the second millennium there were population movements of no lessimport, if on a somewhat smaller scale: The Nilotic migrations into lacustrineeastern Africa and the Oromo expansion into the Ethiopian Highlands inparticular revolutionised the nature of warfare and military organisation intheir respective arenas, and transformed forever the polity itself.