Tens of thousands of Yazidi people were forced to leave their homes.
But younger boys were treated differently.
Captured and taken to camps, these children were forced by ISIL fighters to convert to Islam and undergo training. The boys were fed ideology and taught how to fight and kill.
Al Jazeera spoke to one former prisoner, a 14-year-old Yazidi boy, about his experience being trained at an ISIL camp in the Syrian city of Raqqa.
"Once they showed us the beheading video of the pilots and other videos where they carried out attacks," he said.
"We saw how they were shooting. They brought dolls and they told us how to hold the sword and how to chop off the head."
Though he eventually escaped with his brother, many other young boys remain at the camp, victims of a seemingly never-ending conflict.
Al Jazeera's Victoria Gatenby explains.