- German journalist and author Juergen Todenhoefer journeyed deep into ISIS territory
- He interviewed ISIS fighters, prisoners, and members of the public caught up in the battle for Iraq and Syria
- One ISIS spokesman told Todenhofer: "slavery and beheadings [are] part of our religion"
- ISIS "preparing the largest religious cleansing campaign the world has ever seen," says Todenhoefer
(CNN)Juergen Todenhoefer's journey was a tough one: dangerous, but also eye-opening. The author traveled deep into ISIS territory -- the area they now call their "caliphate" -- visiting Raqqa and Deir Ezzor in Syria, as well as Mosul in Iraq.
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