After fifteen or twenty years, problems arise in polygamous households. There are young men the same age as their father’s youngest wives. If the father cannot afford eunuch guards over a sequestered harem, he has to force the young men to leave.
Every wife who’s not the mother of the young man-to-be-sent-away wants him gone. That leaves more assets for them and their children. Once the young men are gone, competition for household money keeps investments from being made in their educations. They are on their own.
Such young men, usually sons of less favored wives, are driven into the company of other young men evicted for similar reasons. All of them are angry. Few of them have futures. All of them know they have been treated unfairly. They are frustrated because there’s nothing they can do about the unfairness they know will destroy them.
As long as rulers can keep these disaffected, homeless young men focused on hating their neighbors, they are a political asset. First, directing anger at others keeps their own country safer from revolution.
Since wealth and wives are concentrated in the hands of a few, bribery, with money and daughters, keeps the angry young men in line. By bribing a few of these young men, and jailing a few others, the rest are immobilized. Better yet, they may be forced to leave the country, where they become someone else’s problem.
Under-educated, unskilled, and easily led, they are the vanguard of sabotage and invasion in every country that is their enemy. They are carefully taught that every country is their enemy.
Such angry young men see advantages in seeking a glorious end. It’s the only way many of them have to get what they really want; their own harem of seventy two virgins, far more than their father had.
