In normal circumstances, nomads rear a range of animals to make the full use of the various qualities of available grazing. The horse figures primarily as an expensive, almost luxury animal, used for raiding, war, transport, and trade. Its meat and milk provide only an inefficient return in terms of usable protein compared with the quality and quantity of grazing required. As a result, nomads generally keep relatively few horses. However, if warfare becomes a financially attractive proposition, as it did when the Huns came within range of the Roman Empire, then nomads might well start to breed increasing numbers of horses for war—evolving, in the process, into a particular type of military predatory nomadic group. This could never have worked as a subsistence strategy out on the steppe, where the potential proceeds from warfare were so much less.

From Peter Heather’s The Fall of the Roman Empire: A New History, London: Pan Books, 2006 (first published in 2005), p. 328.