The Ottoman empire levied a tax in children on Christian villages. Every year, a certain percentage of the young men were rounded up and sent to Istanbul where they were circumcised, made to recite the magic words that turned them into muslims, and trained in martial disciplines. They were the slave soldiers/administrators who made the empire viable. They propped up the system that oppressed their families and enslaved them.
I think the closest parallel to the yeni cheri (Turkish: new troops, anglicized as janissary would be the TAG ("talented and gifted") programs which cull out the kids whose brains have survived the statist indoctrination so far, subject them to more intensive attention at "governor's schools," and use them as future "leaders." Supporters of the status quo.
Also, not all janissaries were trained as soldiers. The cream of the crop were rather taught to be scholars and administrators.
They eventually wound up dominating, dethroning and even killing Sultans who got in their way.