Ben Farmer, Telegraph, September 29, 2016

Europe faces a generation-long struggle to deal with thousands of battle-hardened jihadists returning as the Islamic State’s caliphate starts to collapse, the EU’s police chief has warned.

An estimated 3,000 European fighters are believed to be with Islamic State in Iraq and Levant (Isil) with officials fearing the coming battle for Mosul will see many try to return home.

Around 850 Britons are thought to have gone to fight in Syria or Iraq, with around 400 still in the country.

Rob Wainwright, director of the European Union’s police agency Europol, told the Wall Street Journal: “I think it will be a generation-long struggle that we face to absorb the return of thousands of foreign fighters, particularly to Western Europe.”

He said their exposure to extreme violence “on top of their radicalized state makes them highly dangerous individuals”.

Isil has lost half its territory in Iraq and its caliphate is shrinking around its twin strongholds of Mosul and Raqqa.

Officials say the flow of jihadists going from Britain to Syria has slowed to a trickle and the number returning has also slowed dramatically, with many expected to fight to the bitter end.

But the Government is in talks with its allies over how to bring to justice British fighters expected to be captured during fighting in the coming months.

Michael Fallon, the defence secretary, said last week: “Partners in the coalition are very clear that their nationals who have gone out to fight and been involved in the most barbaric of crimes should not be allowed to slip through the net without facing justice. We will be reviewing how we each attempt to prosecute our own fighters.”

More than a million people are expected to flee Mosul after an Iraqi army offensive to liberate the city is expected to begin in October, the United Nations said.

Bruno Geddo, chief of the UN’s refugee agency in Iraq said: “Mosul has the potential to be one of the largest manmade disasters for many, many years . . . More than a million could be displaced as a result of the forthcoming offensive.”