To be sure, not all who fight with the Islamic State are committed zealots. When we asked captured Islamic State fighters in Iraq: ‘What is Islam?’ they answered: ‘My life’, but they had little knowledge of the Quran or hadith, and none of Muslim history. Their sense of religion was fused with the vision of a caliphate that kills or subjugates any nonbeliever, but their conversion was not complete. In the face of almost sure execution by the Kurds, most were ready to recant. In one conversation picked up by a Kurdish walkie-talkie, a fighter with a local accent asked for help: ‘My brother has been killed. I am surrounded. Help me take his body away.’ The reply: ‘Perfect, you will join him soon in Paradise.’ The fighter retorted: ‘Come for me. This Paradise, I don’t want.’