Jürgen Todenhöfer interview

Journalist Jürgen Todenhöfer's interview with the German "Islamic State" fighter Christian Emde was released on Wednesday and aired on private TV network RTL.

Filmed in Mosul with masked men carrying guns in the background, Todenhöfer also published the interview on his Facebook page. In an accompanying comment., the journalist said he had only decided to release the video after much thought.

"You can only beat your opponent, if you know them," said Todenhöfer, who was granted safe passage by the IS leadership to research a book about the militant group.

In the 13-minute video clip, the bearded 30-year-old from Solingen admitted that IS had ambitions far beyond its own borders. Already, he said, the group was making inroads in Libya, Egypt, Yemen, and "the so-called Saudi Arabia."

"We say, we have no borders, we have only front lines - which means the expansion will not stop," said Emde.

When asked whether IS "wanted to conquer" Europe one day, for Emde, there was no doubt. "We will conquer Europe one day," he said. "We don't just want to. We will. And we are sure about that."

In his defense of IS - which is thought to control an area larger than Great Britain - Emde assured Todenhöfer that Jews and Christians could worship freely - provided they paid a "protection" tax.

Unlimited genocide

However, he said, Shiite Muslims - who globally number some 150 million and who IS regard as "apostates" - would all be killed unless they converted, even if that meant a genocide of unprecedented proportions.

"100 million, 200 million, 500 million - we don't care about the number," he said. "Every apostate will be killed."

Emde, who during the interview defended beheadings as "part of religion," and slavery as "a progress," said IS would take its fight to the West. In particular, he singled out Germany over weapons shipments to the Kurdish peshmerga.

"If I will return to Germany - I don't know - Only Allah knows," Emde said as the interview ended. "But we will definitely return. It won't be with pleasantries or anything like that, but it will be with our weapons and our fighters - and we will kill everyone who doesn't accept Islam or pay the protection tax."

Germany's RTL television channel broadcast the interview along with other footage of Todenhöfer during his stay in IS-controlled territory.

Summarizing his thoughts to the channel, Todenhöfer described Emde as: "A highly intelligent, dogmatic ideologue - well read, totally brutal, totally unshakeable, and 100 percent convinced that he is doing the right thing."