Jurgen Todenhofer, the first Western reporter to embed with Islamic State fighters and not be killed in the process, spoke to Al Jazeera about his time with the terror group.

Todenhofer lived side by side with the jihadist fighters for ten days in the Islamic State-stronghold city of Mosul, Iraq. He was accompanied only by his son, who served as his cameraman.

“I always asked them about the value of mercy in Islam,” but “I didn’t see any mercy in their behavior,” explained Todenhofer. He added, “Something that I don’t understand at all is the enthusiasm in their plan of religious cleansing, planning to kill the non-believers… They also will kill Muslim democrats because they believe that non-ISIL-Muslims put the laws of human beings above the commandments of God.”

The German reporter then elaborated on how shocked he was about how “willing to kill” the ISIS fighters are. He said that they were ready to commit genocide. “They were talking about [killing] hundreds of millions. They were enthusiastic about it, and I just cannot understand that,” said Todenhofer

He warned that the Islamic State “is much stronger than we think,” and that their recruiting has brought motivated jihadis from across the globe. “Each day, hundreds of new enthusiastic fighters are arriving,” explained Todenhofer. “There is an incredible enthusiasm that I have never seen in any other war zones I have been to.”

The journalist asserted that the U.S.-led bombing campaign was not going to stop the Islamic State and its continuing jihad. He told Al Jazeera that he believed the terror group would only be stopped if fellow Sunni Iraqis would rise up against them.

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