Warning: Disturbing content

Mutassim is nervous. The 16-year-old has never flown in a plane before. He is looking around at the other passengers waiting at the departure gate in Athens airport.

He is unsure of himself, so he mimics their actions, placing his boarding pass inside his passport, and queuing to board.

As the flight is called, the Syrian boy runs through the few phrases of Spanish he's learned. The authorities may ask him questions, and he's travelling on a fake Spanish passport. It's cost more than €3000, bought from a chain of people smugglers who helped him escape from Syria, to Turkey and now into Europe.

Only a month earlier he had been in Raqqa, a member of the so-called Islamic State. The teenager had been assigned to a city hospital, tending to IS fighters and helping the sick. Before that, he was with one of the propaganda units.

But that was another life, one he wants to forget. The airstrikes, the screams, the beheadings, are behind him now. They must remain a secret, as a new start awaits in Germany - but only if the authorities don't discover that he had trained and served as a Lion Cub for the caliphate.

The so-called Islamic State is collapsing. In Syria, Iraq and Libya, it is losing territory. Its ambitions of a global caliphate are unrealised. But perhaps this was predicted, even anticipated. There was a back-up plan, an insurance policy aimed at prolonging its survival long after Raqqa, Sirte and Mosul slipped from its grasp.

First came the grooming, then the recruitment and training to create a new army of child jihadists, who might grow into adult militants. The Islamic State’s next generation of hate.