Your reference to the integration of the conquered reminds me of James C. Scott's studies of the states of Southeast Asia. As he explains it, the limiting factor on the wealth of kings was the number of subjects they had working the land. So when they went to war, it was primarily to capture more people they could enserf. There was actually a regular intergenerational cycle. Grandparents could have been (the equivalent of) serfs, some of their grandchildren might have had some sort of sub-chief of a sub-village position, others might have been conscripted to fight a war to round up more farm labor, while others yet might have run off to the hills to stay out of reach of the state.
Your reference to the integration of the conquered reminds me of James C. Scott's studies of the states of Southeast Asia. As he explains it, the limiting factor on the wealth of kings was the number of subjects they had working the land. So when they went to war, it was primarily to capture more people they could enserf. There was actually a regular intergenerational cycle. Grandparents could have been (the equivalent of) serfs, some of their grandchildren might have had some sort of sub-chief of a sub-village position, others might have been conscripted to fight a war to round up more farm labor, while others yet might have run off to the hills to stay out of reach of the state.