REUTERS/ GETTY Karin von Hippel warned Europe could be hit by ISIS militants

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Karin von Hippel – who served under US General John Allen as part of a special envoy to counter ISIS – claimed as many as 30,000 foreign Daesh fighters from around 100 different countries could spread across the continent once the terror group is crushed in its Iraqi stronghold. Dr von Hippel warned: “I don’t think it will be the beginning of the end. I think once they lose territory in Iraq and Syria and probably Libya… they will likely go back to a more insurgent style operation versus a terrorist group that wants to try and hold onto territory.

TWITTER Karin von Hippel is now director-general of military think tank Royal United Services Institute

There has been about 30,000 foreign fighters that have gone in from about 100 countries to join [ISIS] Karin von Hippel

“There has been about 30,000 foreign fighters that have gone in from about 100 countries to join. Not all of them have joined ISIS, some have joined al-Qaeda and Kurds and other groups, but the vast majority have gone to join ISIS. “These people will disperse. Some of them have already been captured or killed but many will disperse and they'll go to European countries. "They may not go back to where they came from and that is definitely keeping security forces up at night in many, many countries.”

Dr von Hippel – who has also worked for the UN and EU in Kosovo and Somalia – added it was just a matter of time before Daesh is defeated in Iraq's second city, but warned the twisted killers will not go down without a fight. She added: “They will start to leave as they’re outnumbered but they will leave IEDs, they will probably take civilians with them as human shields. So the question in the immediate aftermath is what is the state of the city. "They’re going to be significantly outgunned, and the Iraqis were only ever going to move on Mosul when they are ready.

GETTY Mosul is under the control of ISIS

"There has been talks to re-take Mosul for over a year and so Iraqis really were in charge and wanted to do it when they felt they were ready and got some successes under their belt." The director-general of military think tank Royal United Services Institute (RUSI) added that the next step after Mosul would be to crush any hope militants have of fleeing to the Syrian city of Raqqa.

Battle for Mosul Tue, January 12, 2016 A major offensive to recapture Mosul from ISIS continues. Play slideshow REUTERS 1 of 80 Members of the Iraqi rapid response forces fire missile toward Islamic State militants during a battle between Iraqi forces and Islamic State militants in Somer district of eastern Mosul

GETTY Iraqi forces are currently fighting to push the death cult out of the city