Of all the horrors of this benighted century, the genocide of the Yazidis at the hands of ISIS a decade ago stands out for its extreme brutality and inhumanity. At the time, few people outside the region were aware of the group’s existence; as non-Muslims (Yazidism has pre-Zoroastrian roots), Yazidis were specifically targeted. The world has by now, alas, largely moved on to other atrocities.