The difference between prehistoric warfare and ancient warfare is less one of technology than of organization. The development of the first city-states, and then empires, allowed warfare to change dramatically. Beginning in Mesopotamia, states produced sufficient agricultural surplus that full-time ruling elites and military commanders could emerge. While the bulk of military forces were still farmers, the society could support having them campaigning rather than working the land for a portion of each year. Thus, organized armies developed for the first time.