A grim account of how quickly Christian communities in Syria and Iraq were turned on once ISIS arrived — bad news for religious minorities still living in the region.

• ISIS fighters painted the Arabic letter "N" — for Nasara, meaning Christian — on homes to mark where non-Muslims lived.
• The marked houses became targets, turning neighbors into easy prey.
• Christians who had lived alongside Muslim neighbors for generations, often helping poorer families, said those same neighbors betrayed them the moment ISIS took over.
• The speed of that collapse shows how thin coexistence can be once an armed group gives cover to turn on a minority.

Outlook: Christian populations in Syria and Iraq remain small and exposed, and any new breakdown of order there puts them at risk again.