There is a recurring pattern: The perpetrators are young, Arab men who reside illegally in Europe and have not yet been repatriated. They act alone, armed with a knife, and have learned about jihad online, through WhatsApp groups and other social media networks. Although all “infidels” are considered the enemy, their primary targets are Christians. Two years ago, the Islamic State ordered its followers to attack churches in Spain. Now, it seems that the call is being heeded.