Condemned to the same inhumane punishment was the girl's mother, made to endure the additional and unimaginable horror of helplessly watching the life drain from her daughter's tiny body.

The mother and child were members of Iraq’s Yazidi religious minority. Their captors, members of Islamic State (IS), are said to be German and Iraqi. At the time, Islamic State recruits felt invincible. They taunted the West and ruled over civilians in their territory with cruelty and terror. Four years later, their ‘Caliphate’ had crumbled and the German jihadist, Jennifer W., was facing war crimes charges in her native Munich.

This case set an important precedent, opening the gates for a handful of other charges to be brought against German citizens. The little girl’s mother testified at the trial in Munich: ‘It is very difficult to see your own daughter die in front of your eyes. I want the whole world to know what they have done.’ But the biblical scenes which dominated news cycles when IS first descended on the Yazidis are already fading from memory, and so far, justice for the genocide has not been delivered.

At least 6,000 people from Western Europe abandoned their lives to join Isis’s doomed state-building project, with dozens more from North America and Australasia. Many were killed, but 450 have returned to Britain, 300 to France and 150 to Sweden, whereas several hundred who stuck it out until the end are now stranded in Northern Syria under the watch of Kurdish forces.

So far, the discussions of the fate of these ‘foreign fighters’ has been parochial. Largely absent from an emotive and polarised debate has been the suffering these recruits inflicted on local civilians, none more so than the Yazidi people – whose terrible fate was captured in the chilling words of one UN inquiry: