With testimony drawn from more than 200 interviews with Yazidi survivors--girls, women, boys, and men--recorded during 11 investigative trips to refugee camps in Iraqi Kurdistan. The massacre of the Yazidi people by ISIS was nothing less than genocide. In refugee camps in Iraqi Kurdistan, the authors brought a skilled team to interview more than a hundred ISIS survivors and document what they experienced and saw. These former slaves observed their torturers and know from the inside the secret facilities that ISIS has kept hidden from the world. What their testimony reveals is an organization whose ambition is power, regardless of their claim to be "soldiers of God." Their fighters are paid with sex, money, and the power of life and death over captives. Their promised paradise is here and now, not after death. Men who didn't swear allegiance were executed. Women became slaves for sex or reproduction, and their offspring may still serve the cause. In mobile training camps, the captured children were drugged, indoctrinated, and taught to shoot Kalashnikovs, plant explosives, and handle suicide vests. They are the intended products of the terrorist factory. In this taut, disturbing account, the authors document a utilitarian genocide that still holds an implicit threat to other counties, including those in the West.