NICE, France—Sir Elton John’s enormous cream-colored villa on Mont Boron looms high in the distance, visible from the dingy flats of this cité, or housing project, called Bon Voyage. It’s a different world, and in recent years, a number of young French Muslims left this spot in this city’s northeast to join the so-called Islamic State in Syria.

This was once home to Omar Diaby, who, from his base in Syria, became the biggest recruiter of ISIS fighters in France. He briefly faked his death in Syria, but is now believed to be at large. Another local, 31-year-old Mohamed Lahouaiej-Bouhlel, drove a truck into a crowd of 300,000 in Nice on July 14, 2016, killing 86 people before he died in a hail of bullets.

One young Salafist Muslim, whom I last spoke to three years ago and who knows French fighters from here, was in a more jovial mood than usual when I met him Tuesday at a kebab joint in La Trinité, one of two major Muslim enclaves on this city’s outskirts.

Bachir is smiling. Why? Because thanks to U.S. President Donald Trump pulling troops out of northeast Syria, French ISIS fighters, captured in recent years by Kurdish-led Syrian Democratic Forces (SDF) in northern Syria, are said to be escaping their captors—and rejoining their former comrades in what could mean a renaissance for the once mighty Islamic State.

Between 400 and 450 French ISIS fighters have been detained in Kurdish camps in northeastern Syria. Last week, Turkey launched Operation Peace Spring after Trump gave the de facto go-ahead by moving U.S. troops out of the way. The Kurds, desperate after being abandoned by the U.S., are now aligning themselves with the hated President Bashar al-Assad of Syria and no longer have the manpower to guard their prisons. As The Daily Beast reported, the American forces now withdrawing have had to turn their attention away from pursuing ISIS and focus on the risk that ISIS will be pursuing them.

“ With the collapse of ISIS and the attitude of Turkey against the Kurds, the resurgence of attacks in France is being planned. ” — Christian Estrosi, mayor of Nice, France

Here in Nice, Bachir denies that he is pro-ISIS, but his facial expressions indicate otherwise. “There’s a lot of misinformation about what our brothers are trying to accomplish over there,” he said. “I hope they have a second chance to do some good work, thanks to the U.S.”

And who are some of those ISIS fighters who may live to fight another day and “do some good work”—courtesy of Trump and Turkish President Recep Tayyip Erdogan?

For starters, 35-year-old Adrien Guihal, a French convert to Islam who was part of the infamous and deadly Artigat network, named for a village near Toulouse where extremists—including the terrorist Mohammed Merah, who shot up a Jewish school in Toulouse in 2012—used to meet in a farmhouse.

Guihal was the “voice of ISIS” who claimed responsibility for several major French terrorist attacks. Followers of ISIS on social media say Guihal may have escaped from a Kurdish prison with several other key figures—possibly the equally dangerous Thomas Barnouin—in the chaos that’s followed Trump’s decision to withdraw 1,000 troops from northern Syria.

“With the collapse of ISIS and the attitude of Turkey against the Kurds, the resurgence of attacks in France is being planned,” Christian Estrosi, the mayor of Nice, warned Tuesday. “Jihadists like Adrien Guihal who took up arms against France are destined to reorganize themselves and begin again.”

Guihal, whose nom de guerre is Abu Oussama al-Faransi (which would translate roughly as Father of Osama, the Frenchman) had claimed responsibility for the slaughter in Nice, although direct connections to ISIS were never established, as well as Magnanville, where a policeman and his wife, who also worked for the police, were murdered in front of their toddler, and Saint-Etienne-du-Rouvray, where a would-be holy warrior slit the throat of an aged priest. French Twitter was awash in furious comments about Guihal’s escape. As one poster wrote ironically that Trump and Erdogan “can sleep well tonight” having set such a person free. “Mission accomplished!”

French terrorism expert Jean-Charles Brisard told The Daily Beast that the situation in Syria was “anarchy” and there was no actual confirmation of Guihal’s escape yet.

But Brisard also told the Nice-Matin newspaper that he spotted an encrypted email used by someone familiar with Guihal that indicated “five brothers” had escaped from the Kurdish-held Qamishli prison and one of them was “Abu Oussama al-Faransi,” Guihal’s alias.

Long backed by the U.S. until last week, Kurdish-led troops have held about 10,000 people believed to be part of the Islamic State in 20 small prisons. They’ve also operated camps housing about 70,000 women and children believed to be ISIS relatives.

But they’ve had to take many guards off prison duty to help them fight Turkish forces crossing the border over the past week, leaving the jails vulnerable.

Trump, having precipitated the worst policy disaster of his term so far, has suggested the Kurds are releasing ISIS prisoners to force the U.S. to stay involved in Syria. But as the Kurds are forced to reduce their numbers guarding the ISIS fighters and their families, the prisons become increasingly dangerous for anyone left behind, which is why many nongovernmental organizations have withdrawn their personnel as well. In effect, Trump handed ISIS a “get out of jail free” card.

Last week, the SDF said several ISIS fighters escaped from Qamishli after Turkey bombed it. Hundreds of ISIS relatives broke out of one of the camps, shortly thereafter. One U.S. official told The Washington Post that “multiple Kurdish-run detention facilities were now unguarded and that the U.S. military believed hundreds of detainees had escaped.”

French Prime Minister Édouard Philippe told deputies in the French National Assembly on Tuesday that a resurgence of ISIS is “inevitable,” blaming President Trump for his decision to pull 1,000 troops from Syria.

“This is devastating for our security with the inevitable resurgence of the Islamic State in northeastern Syria and probably also northwest Iraq and so the destabilization of a government that doesn’t need that,” Philippe said.

Trump has been telling his supporters on Twitter that ISIS was completely defeated and the threat was past, but Brisard told The Daily Beast that the notion that ISIS had all but disappeared was not true. What changed was that the ISIS “caliphate” could no longer claim to rule a defined territory. But as a terrorist insurgency, its murderous activities have continued with a vengeance.

“It’s not as if ISIS was really conquered over there and the killing stopped,” Brisard said. “I’ve visited several times over the past year and witnessed hundreds of attacks by ISIS.”

Agit Polat, the spokesman for the Kurdish Democratic Council in France, told OrientXXI magazine that the “betrayal” of the U.S. has “opened the door” for the Turkish invasion.

“They have one main objective: to destroy plural, multi-community and multi-faith government that has been established in northern and eastern Syria. The direct consequence of this annihilation will be the strengthening of jihadism and terrorism.”