I don't think everything can be explained in such a top down way, as if there is a determined ruling class that subjugates a set of passive actors that don't ha

I don't think everything can be explained in such a top down way, as if there is a determined ruling class that subjugates a set of passive actors that don't have any role in the hole story. Society is built by individuals that are ultimately driven by the same things, no matter what is your current place in the dominance hierarchy. Thinking that the average peasant would not engage in aggressive behaviour if it were not for the "ruling class" to provide that incentive fails to explain how the ruling class emerged in the first place. Humans compete. They compete for mates, for prestige, for resources. Harmony and peace require effort to build and sustain, but they pay dividends. Prosperity benefits the rulers too. Paradoxically, harmony and peace in ancient history was often the product of interests of the same ruling classes that engaged in the warring behaviour.