The trade in Yazidi women and girls has created a persistent infrastructure, with a network of warehouses where the victims are held, viewing rooms where they are inspected and marketed, and a dedicated fleet of buses used to transport them.

A total of 5,270 Yazidis were abducted last year, and at least 3,144 are still being held, according to community leaders. To handle them, the Islamic State has developed a detailed bureaucracy of sex slavery, including sales contracts notarized by the ISIS-run Islamic courts. And the practice has become an established recruiting tool to lure men from deeply conservative Muslim societies, where casual sex is taboo and dating is forbidden.

A growing body of internal policy memos and theological discussions has established guidelines for slavery, including a lengthy how-to manual issued by the Islamic State Research and Fatwa Department just last month. Repeatedly, the ISIS leadership has emphasized a narrow and selective reading of the Quran and other religious rulings to not only justify violence, but also to elevate and celebrate each sexual assault as spiritually beneficial, even virtuous.

“Every time that he came to rape me, he would pray,” said F, a 15-year-old girl who was captured on the shoulder of Mount Sinjar one year ago and was sold to an Iraqi fighter in his 20s. Like some others interviewed by The New York Times, she wanted to be identified only by her first initial because of the shame associated with rape.