– After being injured fighting the Syrian government, 31-year-old Mohannad reached his home in Frankfurt, Germany, with a simple plan: rest, recuperate, then rejoin the fight with the Islamic State of Iraq and the Levant (ISIL).

As related in German newspaper accounts, which by law couldn't identify him by his full name, Mohannad even transferred the equivalent of $6,800 to a Syrian bank for use by the terror organization. With that as evidence that Mohannad was supporting a terrorist organization, German authorities seized his passport and prevented him from returning to Turkey — the jumping-off point for radicals seeking to join the fight in Syria.

But Mohannad was the exception. Officials concede that they rarely have such an extensive file against so-called "jihadi tourists" to stop them from reaching Turkey — and Syria beyond.

At least 320 Germans and more than 2,000 other Europeans are thought to have made the trip — so many that Turkish Prime Minister Recep Tayyip Erodgan has asked European nations to stop their citizens wanting to join the fight in Syria and now Iraq from traveling to Turkey.

"Preventing people from traveling is really difficult," said Stefan Mayer, spokesman for Germany's national intelligence agency. "We need actionable evidence, evidence we can use in court. Unless we can prove they've worked for a foreign terror organization before, the law doesn't make it easy to stop someone from making the journey."

German courts consistently have returned seized passports before the bearers have broken any laws.

European Union counterterrorism coordinator Gilles de Kerchove this month noted that the phenomenon of young Muslims leaving Europe to fight elsewhere is not new. But the current numbers dwarf previous migrations. He called the current flow "huge."

"Compared to previous jihads, it's unprecedented," he said.

The trend is openly discussed in Germany, France, the United Kingdom, the Netherlands and Italy. Europe has long needed immigrant labor, but it has done little to integrate those who come from Muslim regions — North Africa, Pakistan and the Middle East. Their children often grow up without close ties to their adopted nations and end up finding a sense of community online and in the radical splinters of Islam set up to prey upon the lost.

Claudia Dantschke, a German specialist in Islam who tries to identify and counsel families where the young people are at risk of choosing the fight, said officials struggled to keep up with the increased intensity of recruiting actions.

"The public awareness for the problem of young people from Germany joining the jihad has increased, so more families are turning to us for help," she said.

But that search for help is countered by what she said was "a massive increase in propaganda from recruiters for ISIL," triggered by the group's expansion in Syria and Iraq, where in the past three weeks it has seized control of major cities.

"A higher number of young people [are] leaving the country with the aim to join the group," Dantschke said.

Perhaps most worrying to anti-terror experts is that ISIL is now thought to have a war chest worth from several hundred million dollars up to $2 billion. The funds allow ISIL to better equip, and better maintain, a larger force.