In the summer of 2011, three French ex-convicts met in Yemen to talk about unleashing death and terror on the streets of Paris.
The trio was part of a crew of jihadis who radicalised together in the Buttes-Chaumont neighborhood of Paris a decade earlier. All three had been convicted of serious crimes. But they were at large thanks to a problem that gets scant attention in France and elsewhere in Europe: lenient sentencing policies for people convicted of terrorism and other violent crimes.
Peter Cherif, the son of Afro-Caribbean and Tunisian immigrants, was the dominant figure at the meeting. In 2004, U.S. troops had captured him while he was fighting for al-Qaida in Iraq. After his return to France, he served just 18 months in jail before he won release pending trial.
By the time the court imposed a five-year sentence on Cherif, he had fled to Yemen to join the al-Qaida offshoot there. US courts have sent terrorists found guilty of comparable offenses to maximum-security prisons for decades or life.
Intelligence officials say Cherif was visited in Yemen by Salim Benghalem, who was radicalised in prison by another Buttes-Chaumont jihadi who fought in Iraq. Convicted for a murder, Benghalem had served about six years before he was back on the street.
Cherif's other visitor had done a mere 20 months behind bars for his role in sending young Parisian suicide bombers to kill US troops in Iraq. His name: Cherif Kouachi.
In Yemen, the three discussed attacks on US targets in France and on a satirical magazine that had published cartoons of the Prophet Muhammad, investigators say. Peter Cherif helped provide Kouachi with cash and a few days of al-Qaida training, according to French and U.S. intelligence officials.
Four years later, Kouachi hit the big time. He massacred journalists at Charlie Hebdo magazine in January, dying along with his brother Said after a rampage across Paris that killed 17 people and caused international outcry.
Although the Kouachi brothers got most of the public attention, others in their crew have attained frontline roles in terrorist groups. Their story underscores a worrisome reality at a time of unprecedented radicalisation among youth in Europe. European law enforcement is good at catching terrorists, but not so good at keeping them locked up. The problem is evident in France and Belgium, two nations that have seen the largest number of extremists travel to Syria to fight.
"Penal policies have not adapted to the reality of the terrorist threat," said Louis Caprioli, a former counterterror chief of France's domestic spy agency now with a private security consulting group.
"Terrorists are treated like common criminals when it comes to sentencing, even if they are repeat offenders," he said. "We have to take these guys off the streets. The philosophy has been to rescue the individual rather than to protect the society."
Tilt toward rehabilitation
If prison terms were tougher, the January attacks in Paris might never have happened. Consider the trajectory of Amedy Coulibaly, a 32-year-old Frenchman who killed hostages at a Jewish grocery in coordination with the Charlie Hebdo massacre.
Coulibaly's criminal career began at age 18. In 2004, he was sentenced to six years for armed robberies and drug dealing. While in jail, he met Cherif Kouachi and other terrorists and adopted their extremist views. Soon after their release, French police arrested Coulibaly and Kouachi for plotting to storm a prison and free a convicted terrorist bomb maker.
Charges were dropped against Kouachi. Coulibaly was convicted of illegal arms possession in the jailbreak plot, but sentenced to only five years even though he was a repeat offender linked to known terrorists. By May 2014 he was out again. Eight months later, he was dead – along with four victims at the Jewish grocery and a policewoman he gunned down earlier.
French prosecutors have strong tools for putting terror suspects in preventive detention and convicting them at trial. But when it comes to punishment, judicial authorities have less power than their US counterparts, who win long sentences for crimes such as "material support" of terrorism.
In France, the main weapon in the judicial arsenal is the crime of terrorist conspiracy, which generally brings a maximum of 10 years. Thanks to probation and good behavior policies, people convicted of conspiracy often serve about half their terms, experts say.
"It's a real problem," said Mohamed Douhane, a French police commandant and secretary general of the Synergie Officiers police union. "We police officers don't understand the weak sentences and the fact that convicts don't serve their entire sentences."
After the Paris attacks, public scrutiny focused on intelligence breakdowns that had caused police to curtail their monitoring of the Kouachis and Coulibaly. In May, the French parliament approved legislation giving authorities vast new surveillance powers – and raising concerns about civil liberties. Authorities have also sped up a project to segregate convicted terrorists in prison to prevent radicalisation of common criminals.
There has been little movement, however, toward beefed-up punishment. Although special investigative magistrates prosecute terrorism cases, courts continue to handle trials, sentencing and their aftermath much like other cases.
"The main difference is in the degree of flexibility in the sentence for parole, semi-conditional liberty, etc.," said Agnes Thibault-Lecuivre, a spokeswoman for Paris prosecutors. "It is a question we are asking ourselves: Should the sentences for terrorism be longer?"
A report by Europol, the European police alliance, found that in 2012 the average sentence for terrorism in France was five years – which often meant about two and a half years actually behind bars. The average terrorism sentence was six years in Germany and Britain, and five years in Belgium, according to the study. Sentences tended to be tougher in Spain, where Basque and Islamic terrorism have killed hundreds.
In 2013, the average prison term for terrorist offenses in France and Britain rose to seven and nine years, respectively, and declined to four years in Germany, according to Europol.
A deep-rooted judicial philosophy in Europe emphasises rehabilitation. In a major trial that ended in February, a Belgian court convicted 45 members of Sharia4Belgium, an extremist group that sent dozens of fighters to Syria. Most of the defendants remain in Syria, where some allegedly committed terrorist attacks and atrocities.
The sentences ranged from three to 15 years, and some were suspended. Fouad Belkacem, the group's charismatic chief based in Antwerp, got 12 years. He had previously been convicted of crimes including drug trafficking and incitement of hatred.
"A 12-year sentence is nothing for a man like that," complained Ozana Rodrigues Viana, a defendant's mother, in an interview with La Libre Belgique newspaper. "He's a terrorist. But Belgium doesn't want to understand a thing … In Belgium, prison is like a hotel."
US courts have dealt far more harshly with defendants convicted of joining overseas terrorist groups.
John Walker Lindh, the so-called American Taliban, is serving 20 years. A group of Virginia militants who trained in Pakistani terror camps – but did not commit violent acts – got sentences as long as 20 years in 2005. Two leaders of that Virginia cell – one a cleric based in the United States – went to prison for life. And a US court gave a life sentence in 2009 to a Swedish al-Qaida operative who set up a terror training compound in Oregon.
‘Open-bar jihad'
Some European officials defend the restrained approach, contrasting it with what they see as harsh sentences and mass incarceration in the United States.
"In most European countries, we don't do that," said Eric Van Der Sypt, a veteran counterterror prosecutor in Belgium. "The only thing that you obtain is protection of society, not rehabilitation of individual."
But some police and intelligence officials insist it is time to do more. European terrorists pose a worldwide danger because their passports enable easy travel to the United States and elsewhere.
Police are arresting repeat offenders, veterans of a quarter-century of shifting hot spots: Algeria and Afghanistan in the 1990s, US-occupied Iraq in the 2000s, and Syria today.
"Some are caught for the second or third time," said Bernard Squarcini, a former director of France's domestic spy agency. "If they keep getting out, we will have to worry about them until they are grandfathers."
During their stints in prison, convicted terrorists grow more radical and recruit common criminals, exchanging expertise with them, Squarcini said.
Until a few years ago, European countries relied on aggressive surveillance to make up for the limited prison terms. The accelerated pace of radicalisation, officials say, upended that balance. There are increasingly too many suspects to watch, and too many of them gain hands-on experience.
Thousands of Europeans have gone to Syria to fight, most of them joining the Islamic State. The biggest contingent is French: more than 1,400. At least 350 Belgians make up the largest proportional group of foreign fighters.
The new, easy-to-reach battleground differs from al-Qaida's secret compounds in Pakistan. The Islamic State's priority is conquest of territory. Unlike al-Qaida, it does not have an external operations unit that trains militants for terror attacks against Western targets, according to intelligence officials.
Fighters returning from battlefields of Syria and Iraq are more likely to plot on their own. Officials said the leaders of the Islamic State gave their blessing to several foiled plots in Europe proposed by foreign fighters – without getting involved in details.
"We believe the plots had Islamic State approval, but were thought up by the Westerners," said a senior French counterterror official, who requested anonymity because he is not authorised to speak publicly. "What we are dealing with now is open-bar jihad. Do what you want, where you want, when you want, how you want."
In January, Belgian fighters with the Islamic State came home from Syria to prepare an attack on police, authorities say. European and US intelligence got wind of the plot and tracked the suspects. Two died in a shootout with a SWAT team in the city of Verviers.
A real-life video game
While prison sentences remain low, the threat rises. The young men and women who journey to Syria and Iraq quickly end up in combat. Many participate in or become inured to the atrocities – beheadings, torture, rape – that the Islamic State uses as systematic tactics.
"It's like entering a real-life video game: real guns, real people, real blood," said Supt. Alain Grignard of the Belgian federal police. "You develop a feeling of power like you've never had. You come back to your neighborhood full of that power. You are ready to fight the cops. You are drunk on that power, drugged on that violence. It's very dangerous."
Law enforcement officials say it remains a challenge to prove a defendant committed specific acts of terrorism overseas. Last year, a Belgian court sentenced a jihadi to an unusually stiff term of 18 years because he admitted to participating in a deadly ambush of African peacekeeping troops in Somalia.
Investigators also try to capitalise on the self-destructive propensity of militants to leave an incriminating digital trail.
"In the beginning, the first thing they would do when they got to Syria was post a photo on Facebook posing with an AK–47," said Van Der Sypt, the Belgian prosecutor. "With their Armani T-shirts, looking very Western, saying ‘I'm here. I'm a warrior.'"
The barrage of photos, videos and messages reached such a volume last year that the Islamic State urged foreign fighters to curtail their use of social media. Chiefs warned that militants put themselves at risk of being tracked or prosecuted, but the directive didn't have a big impact, according to French and Belgian officials.
In this anarchic subculture, relatively young veterans go far.
More than a decade ago, Boubaker el Hakim was the first of the Buttes-Chaumont crew to reach Iraq. Before the 2003 US invasion, he gave a French radio station an interview in Baghdad, calling on his potes (buddies) back in Paris to join him and "Go boom!"
El Hakim was arrested in 2005. His brother died in combat in Iraq. In 2008, a French court convicted El Hakim of terrorist conspiracy along with Cherif Kouachi and five others involved in the Iraq jihad.
El Hakim did a seven-year term, including time served: the longest sentence. He rapidly returned to the fray: He joined militants in Tunisia. In 2013, he released a video taking credit for the assassinations of two Tunisian political leaders. The 31-year-old El Hakim is now in Syria with the Islamic State, intelligence officials say.
He is one of at least six of the Buttes-Chaumont crew who have subsequently been arrested or investigated again for terrorism.
A soft-spoken, tormented terrorist
The remarkable odyssey of Cherif, now 32, also began in northeast Paris near Buttes-Chaumont Park, which has rolling hills and a waterfall.
The neighbourhood mixes young professionals, a Jewish community and working-class Muslims. Cherif was not raised as a practicing Muslim, and he had a taste for McDonald's, rap music, American action films. By his teen years, he was in trouble for drugs, assault and robbery.
Still, the broad-shouldered youth showed signs of drive and independence. He enlisted in the army, hoping to become a paratrooper. In 2002, he started going out with a Jewish woman he had known since middle school. The relationship was unusual because of the virulent anti-Semitism among many young Muslims in France.
Cherif's girlfriend was resolutely Western in lifestyle. This reporter interviewed her in 2006, agreeing to withhold her name for her safety.
The girlfriend said Cherif was protective and affectionate. She said they had long conversations about politics. He told her about his sympathy for the Palestinians; she told him about the experiences of her relatives in Israel.
"He never said anything anti-Jewish," the girlfriend said. "I have always had many religions around me, and I like it like that."
Cherif began a disastrous slide, however. An injury forced him out of the Army. In 2003, he and a dozen friends (the youngest was 13) became disciples of Farid Benyettou, 23, a self-styled ideologue from the neighborhood. Peter Cherif first recruited Cherif Kouachi and brought him to religious courses taught by Benyettou, according to French court documents.
Although Cherif did not mistreat his girlfriend, he and the others vandalized Jewish restaurants with rocks and Molotov cocktails, and assaulted a Jewish man in the street, breaking his nose, according to court documents. The youths took part in protests against the US invasion of Iraq, catching the attention of police intelligence officers as they prayed in the street wearing basketball shoes and Islamic garb.
With no training beyond workouts in the park, the crew rushed into holy war. Most traveled to Syria, using the cover of study in Koranic schools in Damascus, and slipped across the border to fight for al-Qaida in Iraq, the forerunner of the Islamic State.
Three of the youths died. Cherif was wounded twice battling U.S. Marines in Fallujah, where he helped a Tunisian fighter firing a rocket-launcher, according to his later testimony.
"I was so close to the Americans that I could almost see them with the naked eye," Cherif testified.
American troops captured him in December 2004 and put him in Abu Ghraib prison. An Iraqi court sentenced him to 15 years for illegal entry into the country. In March of 2007, masked al-Qaida militants stormed a prison near Mosul and freed Cherif and about 150 others.
Spending another year in the terror underworld, Cherif met militants from Saudi Arabia and Yemen and helped fighters reach the battlefield from Syria, French court documents say. He remained in contact with his mother and girlfriend by phone and Internet.
In February 2008, a weary Cherif went home to France and surrendered to police. Based on intercepted communications, his statements and the testimony of accomplices, he was charged with terrorist conspiracy. But he told authorities he had repented and deserved a second chance.
"He wasn't a maniac," said Olivier Foks, a lawyer for Cherif. "He spoke softly, expressed himself well. If he was someone who had terrorist intentions at that time, he must have had the talent of a Hollywood actor … He was liberated because he convinced the judge, as he had convinced me."
Cherif spent 18 months in jail before the judge approved his release pending trial in July 2009. During his trial in early 2011, Cherif told his lawyer he could not stand the idea of being behind bars again. Foks predicted imprisonment would be brief, especially considering time served.
The lawyer was right. Despite the evidence of al-Qaida activity and battlefield combat, the court handed down a five-year sentence in March 2011.
But Cherif was already gone. He fled to Yemen, probably using contacts from his past sojourn in the Middle East, according to French intelligence officials.
Al-Qaida's Frenchman in Yemen
The Yemen-based al-Qaida in the Arabian Peninsula is one of the small, sophisticated al-Qaida offshoots that remain determined to strike the West.
In contrast to jihadi hotspots in South Asia and North Africa, very few French militants have gone to Yemen to join AQAP. Cherif became the first Frenchman active in the group's external operations branch, intelligence officials say.
Investigators suspect that Cherif's presence in Yemen was the reason for the trip by Kouachi and Benghalem, who spent about three weeks there in late July and August of 2011.
Although Cherif has not been charged in the Paris plot, French and US counterterror officials believe he played a key support role.
"We think Cherif is the guy who gave Kouachi the money and instructions from al-Qaida," said the senior French counterterror official. "What we fear is that Frenchmen like Peter Cherif in Yemen and … in Syria are the ones in charge of terrorist missions targeting France."
French investigators suspect Cherif helped Kouachi get brief training from al- Qaida in the Arabian Peninsula during the visit to Yemen. U.S. intelligence officials believe the al-Qaida offshoot also provided $20,000 to Kouachi to fund the Charlie Hebdo plot, but they say the group's involvement appears to have been limited.
Kouachi received "a general directive about going after those who insulted the prophet," said a senior US intelligence official familiar with the case. "Charlie Hebdo fits that. I have yet to see more information about hands-on management or command and control by AQAP. There was some type of engagement or meeting in Yemen, and he expressed a desire to take action. AQAP blessed it."
During his rampage in Paris, Kouachi told a journalist by phone that he had acted on the direct orders of Anwar al-Awlaki, the group's US-born ideologue, who was killed in Yemen in September 2011. But investigators have not confirmed that he actually met Awlaki, according to Thibault-Lecuivre, the prosecutors' spokeswoman.
French investigators are also looking at Benghalem's possible links to the case, officials said. They believe "an attack on US interests in France was discussed by Benghalem during the meetings with al-Qaida" in Yemen, Thibault-LeCuivre said. "But the attack didn't happen."
Like the others, Benghalem had exploited the legal system. He had racked up arrests for robbery, assault, guns and drugs by 2001, when he and an accomplice concealed guns in traditional djellabah robes and opened fire on gang rivals in a Paris housing project. One man died.
After a year on the run in Algeria, Benghalem returned and was convicted of attempted murder because evidence showed his gunshots missed the victim. Benghalem served only about half an 11-year sentence, authorities say. In prison, he radicalized under the influence of his cellmate: a Buttes-Chaumont homeboy who had lost an eye and an arm in the battle of Fallujah, French intelligence officials said.
The Charlie Hebdo case suggests that bonds formed in French streets and jails were more crucial than al-Qaida strategists, according to counterterror experts.
"These guys are not sleepers," said Marc Sageman, a former CIA officer and scholar on terrorism. "It's a homegrown, bottom-up attack. It's a far more complex story than calling it an AQAP attack."
Today, French and US intelligence officials believe Cherif remains active with al-Qaida in Yemen.
Benghalem, meanwhile, found refuge in Syria with the Islamic State, intelligence officials say. The U.S. State Department publicly designated him as a terrorist last year, alleging that he presides over executions as a member of an Islamic law panel.
The career criminal, authorities say, has become a judge.
This story was co-published with The Daily Beast.
Read more of Sebastian Rotella's coverage of international terrorism.
ProPublica is a Pulitzer Prize-winning investigative newsroom.
The trio was part of a crew of jihadis who radicalised together in the Buttes-Chaumont neighborhood of Paris a decade earlier. All three had been convicted of serious crimes. But they were at large thanks to a problem that gets scant attention in France and elsewhere in Europe: lenient sentencing policies for people convicted of terrorism and other violent crimes.
Peter Cherif, the son of Afro-Caribbean and Tunisian immigrants, was the dominant figure at the meeting. In 2004, U.S. troops had captured him while he was fighting for al-Qaida in Iraq. After his return to France, he served just 18 months in jail before he won release pending trial.
By the time the court imposed a five-year sentence on Cherif, he had fled to Yemen to join the al-Qaida offshoot there. US courts have sent terrorists found guilty of comparable offenses to maximum-security prisons for decades or life.
Intelligence officials say Cherif was visited in Yemen by Salim Benghalem, who was radicalised in prison by another Buttes-Chaumont jihadi who fought in Iraq. Convicted for a murder, Benghalem had served about six years before he was back on the street.
Cherif's other visitor had done a mere 20 months behind bars for his role in sending young Parisian suicide bombers to kill US troops in Iraq. His name: Cherif Kouachi.
In Yemen, the three discussed attacks on US targets in France and on a satirical magazine that had published cartoons of the Prophet Muhammad, investigators say. Peter Cherif helped provide Kouachi with cash and a few days of al-Qaida training, according to French and U.S. intelligence officials.
Four years later, Kouachi hit the big time. He massacred journalists at Charlie Hebdo magazine in January, dying along with his brother Said after a rampage across Paris that killed 17 people and caused international outcry.
Although the Kouachi brothers got most of the public attention, others in their crew have attained frontline roles in terrorist groups. Their story underscores a worrisome reality at a time of unprecedented radicalisation among youth in Europe. European law enforcement is good at catching terrorists, but not so good at keeping them locked up. The problem is evident in France and Belgium, two nations that have seen the largest number of extremists travel to Syria to fight.
"Penal policies have not adapted to the reality of the terrorist threat," said Louis Caprioli, a former counterterror chief of France's domestic spy agency now with a private security consulting group.
"Terrorists are treated like common criminals when it comes to sentencing, even if they are repeat offenders," he said. "We have to take these guys off the streets. The philosophy has been to rescue the individual rather than to protect the society."
Tilt toward rehabilitation
If prison terms were tougher, the January attacks in Paris might never have happened. Consider the trajectory of Amedy Coulibaly, a 32-year-old Frenchman who killed hostages at a Jewish grocery in coordination with the Charlie Hebdo massacre.
Coulibaly's criminal career began at age 18. In 2004, he was sentenced to six years for armed robberies and drug dealing. While in jail, he met Cherif Kouachi and other terrorists and adopted their extremist views. Soon after their release, French police arrested Coulibaly and Kouachi for plotting to storm a prison and free a convicted terrorist bomb maker.
Charges were dropped against Kouachi. Coulibaly was convicted of illegal arms possession in the jailbreak plot, but sentenced to only five years even though he was a repeat offender linked to known terrorists. By May 2014 he was out again. Eight months later, he was dead – along with four victims at the Jewish grocery and a policewoman he gunned down earlier.
French prosecutors have strong tools for putting terror suspects in preventive detention and convicting them at trial. But when it comes to punishment, judicial authorities have less power than their US counterparts, who win long sentences for crimes such as "material support" of terrorism.
In France, the main weapon in the judicial arsenal is the crime of terrorist conspiracy, which generally brings a maximum of 10 years. Thanks to probation and good behavior policies, people convicted of conspiracy often serve about half their terms, experts say.
"It's a real problem," said Mohamed Douhane, a French police commandant and secretary general of the Synergie Officiers police union. "We police officers don't understand the weak sentences and the fact that convicts don't serve their entire sentences."
After the Paris attacks, public scrutiny focused on intelligence breakdowns that had caused police to curtail their monitoring of the Kouachis and Coulibaly. In May, the French parliament approved legislation giving authorities vast new surveillance powers – and raising concerns about civil liberties. Authorities have also sped up a project to segregate convicted terrorists in prison to prevent radicalisation of common criminals.
There has been little movement, however, toward beefed-up punishment. Although special investigative magistrates prosecute terrorism cases, courts continue to handle trials, sentencing and their aftermath much like other cases.
"The main difference is in the degree of flexibility in the sentence for parole, semi-conditional liberty, etc.," said Agnes Thibault-Lecuivre, a spokeswoman for Paris prosecutors. "It is a question we are asking ourselves: Should the sentences for terrorism be longer?"
A report by Europol, the European police alliance, found that in 2012 the average sentence for terrorism in France was five years – which often meant about two and a half years actually behind bars. The average terrorism sentence was six years in Germany and Britain, and five years in Belgium, according to the study. Sentences tended to be tougher in Spain, where Basque and Islamic terrorism have killed hundreds.
In 2013, the average prison term for terrorist offenses in France and Britain rose to seven and nine years, respectively, and declined to four years in Germany, according to Europol.
A deep-rooted judicial philosophy in Europe emphasises rehabilitation. In a major trial that ended in February, a Belgian court convicted 45 members of Sharia4Belgium, an extremist group that sent dozens of fighters to Syria. Most of the defendants remain in Syria, where some allegedly committed terrorist attacks and atrocities.
The sentences ranged from three to 15 years, and some were suspended. Fouad Belkacem, the group's charismatic chief based in Antwerp, got 12 years. He had previously been convicted of crimes including drug trafficking and incitement of hatred.
"A 12-year sentence is nothing for a man like that," complained Ozana Rodrigues Viana, a defendant's mother, in an interview with La Libre Belgique newspaper. "He's a terrorist. But Belgium doesn't want to understand a thing … In Belgium, prison is like a hotel."
US courts have dealt far more harshly with defendants convicted of joining overseas terrorist groups.
John Walker Lindh, the so-called American Taliban, is serving 20 years. A group of Virginia militants who trained in Pakistani terror camps – but did not commit violent acts – got sentences as long as 20 years in 2005. Two leaders of that Virginia cell – one a cleric based in the United States – went to prison for life. And a US court gave a life sentence in 2009 to a Swedish al-Qaida operative who set up a terror training compound in Oregon.
‘Open-bar jihad'
Some European officials defend the restrained approach, contrasting it with what they see as harsh sentences and mass incarceration in the United States.
"In most European countries, we don't do that," said Eric Van Der Sypt, a veteran counterterror prosecutor in Belgium. "The only thing that you obtain is protection of society, not rehabilitation of individual."
But some police and intelligence officials insist it is time to do more. European terrorists pose a worldwide danger because their passports enable easy travel to the United States and elsewhere.
Police are arresting repeat offenders, veterans of a quarter-century of shifting hot spots: Algeria and Afghanistan in the 1990s, US-occupied Iraq in the 2000s, and Syria today.
"Some are caught for the second or third time," said Bernard Squarcini, a former director of France's domestic spy agency. "If they keep getting out, we will have to worry about them until they are grandfathers."
During their stints in prison, convicted terrorists grow more radical and recruit common criminals, exchanging expertise with them, Squarcini said.
Until a few years ago, European countries relied on aggressive surveillance to make up for the limited prison terms. The accelerated pace of radicalisation, officials say, upended that balance. There are increasingly too many suspects to watch, and too many of them gain hands-on experience.
Thousands of Europeans have gone to Syria to fight, most of them joining the Islamic State. The biggest contingent is French: more than 1,400. At least 350 Belgians make up the largest proportional group of foreign fighters.
The new, easy-to-reach battleground differs from al-Qaida's secret compounds in Pakistan. The Islamic State's priority is conquest of territory. Unlike al-Qaida, it does not have an external operations unit that trains militants for terror attacks against Western targets, according to intelligence officials.
Fighters returning from battlefields of Syria and Iraq are more likely to plot on their own. Officials said the leaders of the Islamic State gave their blessing to several foiled plots in Europe proposed by foreign fighters – without getting involved in details.
"We believe the plots had Islamic State approval, but were thought up by the Westerners," said a senior French counterterror official, who requested anonymity because he is not authorised to speak publicly. "What we are dealing with now is open-bar jihad. Do what you want, where you want, when you want, how you want."
In January, Belgian fighters with the Islamic State came home from Syria to prepare an attack on police, authorities say. European and US intelligence got wind of the plot and tracked the suspects. Two died in a shootout with a SWAT team in the city of Verviers.
A real-life video game
While prison sentences remain low, the threat rises. The young men and women who journey to Syria and Iraq quickly end up in combat. Many participate in or become inured to the atrocities – beheadings, torture, rape – that the Islamic State uses as systematic tactics.
"It's like entering a real-life video game: real guns, real people, real blood," said Supt. Alain Grignard of the Belgian federal police. "You develop a feeling of power like you've never had. You come back to your neighborhood full of that power. You are ready to fight the cops. You are drunk on that power, drugged on that violence. It's very dangerous."
Law enforcement officials say it remains a challenge to prove a defendant committed specific acts of terrorism overseas. Last year, a Belgian court sentenced a jihadi to an unusually stiff term of 18 years because he admitted to participating in a deadly ambush of African peacekeeping troops in Somalia.
Investigators also try to capitalise on the self-destructive propensity of militants to leave an incriminating digital trail.
"In the beginning, the first thing they would do when they got to Syria was post a photo on Facebook posing with an AK–47," said Van Der Sypt, the Belgian prosecutor. "With their Armani T-shirts, looking very Western, saying ‘I'm here. I'm a warrior.'"
The barrage of photos, videos and messages reached such a volume last year that the Islamic State urged foreign fighters to curtail their use of social media. Chiefs warned that militants put themselves at risk of being tracked or prosecuted, but the directive didn't have a big impact, according to French and Belgian officials.
In this anarchic subculture, relatively young veterans go far.
More than a decade ago, Boubaker el Hakim was the first of the Buttes-Chaumont crew to reach Iraq. Before the 2003 US invasion, he gave a French radio station an interview in Baghdad, calling on his potes (buddies) back in Paris to join him and "Go boom!"
El Hakim was arrested in 2005. His brother died in combat in Iraq. In 2008, a French court convicted El Hakim of terrorist conspiracy along with Cherif Kouachi and five others involved in the Iraq jihad.
El Hakim did a seven-year term, including time served: the longest sentence. He rapidly returned to the fray: He joined militants in Tunisia. In 2013, he released a video taking credit for the assassinations of two Tunisian political leaders. The 31-year-old El Hakim is now in Syria with the Islamic State, intelligence officials say.
He is one of at least six of the Buttes-Chaumont crew who have subsequently been arrested or investigated again for terrorism.
A soft-spoken, tormented terrorist
The remarkable odyssey of Cherif, now 32, also began in northeast Paris near Buttes-Chaumont Park, which has rolling hills and a waterfall.
The neighbourhood mixes young professionals, a Jewish community and working-class Muslims. Cherif was not raised as a practicing Muslim, and he had a taste for McDonald's, rap music, American action films. By his teen years, he was in trouble for drugs, assault and robbery.
Still, the broad-shouldered youth showed signs of drive and independence. He enlisted in the army, hoping to become a paratrooper. In 2002, he started going out with a Jewish woman he had known since middle school. The relationship was unusual because of the virulent anti-Semitism among many young Muslims in France.
Cherif's girlfriend was resolutely Western in lifestyle. This reporter interviewed her in 2006, agreeing to withhold her name for her safety.
The girlfriend said Cherif was protective and affectionate. She said they had long conversations about politics. He told her about his sympathy for the Palestinians; she told him about the experiences of her relatives in Israel.
"He never said anything anti-Jewish," the girlfriend said. "I have always had many religions around me, and I like it like that."
Cherif began a disastrous slide, however. An injury forced him out of the Army. In 2003, he and a dozen friends (the youngest was 13) became disciples of Farid Benyettou, 23, a self-styled ideologue from the neighborhood. Peter Cherif first recruited Cherif Kouachi and brought him to religious courses taught by Benyettou, according to French court documents.
Although Cherif did not mistreat his girlfriend, he and the others vandalized Jewish restaurants with rocks and Molotov cocktails, and assaulted a Jewish man in the street, breaking his nose, according to court documents. The youths took part in protests against the US invasion of Iraq, catching the attention of police intelligence officers as they prayed in the street wearing basketball shoes and Islamic garb.
With no training beyond workouts in the park, the crew rushed into holy war. Most traveled to Syria, using the cover of study in Koranic schools in Damascus, and slipped across the border to fight for al-Qaida in Iraq, the forerunner of the Islamic State.
Three of the youths died. Cherif was wounded twice battling U.S. Marines in Fallujah, where he helped a Tunisian fighter firing a rocket-launcher, according to his later testimony.
"I was so close to the Americans that I could almost see them with the naked eye," Cherif testified.
American troops captured him in December 2004 and put him in Abu Ghraib prison. An Iraqi court sentenced him to 15 years for illegal entry into the country. In March of 2007, masked al-Qaida militants stormed a prison near Mosul and freed Cherif and about 150 others.
Spending another year in the terror underworld, Cherif met militants from Saudi Arabia and Yemen and helped fighters reach the battlefield from Syria, French court documents say. He remained in contact with his mother and girlfriend by phone and Internet.
In February 2008, a weary Cherif went home to France and surrendered to police. Based on intercepted communications, his statements and the testimony of accomplices, he was charged with terrorist conspiracy. But he told authorities he had repented and deserved a second chance.
"He wasn't a maniac," said Olivier Foks, a lawyer for Cherif. "He spoke softly, expressed himself well. If he was someone who had terrorist intentions at that time, he must have had the talent of a Hollywood actor … He was liberated because he convinced the judge, as he had convinced me."
Cherif spent 18 months in jail before the judge approved his release pending trial in July 2009. During his trial in early 2011, Cherif told his lawyer he could not stand the idea of being behind bars again. Foks predicted imprisonment would be brief, especially considering time served.
The lawyer was right. Despite the evidence of al-Qaida activity and battlefield combat, the court handed down a five-year sentence in March 2011.
But Cherif was already gone. He fled to Yemen, probably using contacts from his past sojourn in the Middle East, according to French intelligence officials.
Al-Qaida's Frenchman in Yemen
The Yemen-based al-Qaida in the Arabian Peninsula is one of the small, sophisticated al-Qaida offshoots that remain determined to strike the West.
In contrast to jihadi hotspots in South Asia and North Africa, very few French militants have gone to Yemen to join AQAP. Cherif became the first Frenchman active in the group's external operations branch, intelligence officials say.
Investigators suspect that Cherif's presence in Yemen was the reason for the trip by Kouachi and Benghalem, who spent about three weeks there in late July and August of 2011.
Although Cherif has not been charged in the Paris plot, French and US counterterror officials believe he played a key support role.
"We think Cherif is the guy who gave Kouachi the money and instructions from al-Qaida," said the senior French counterterror official. "What we fear is that Frenchmen like Peter Cherif in Yemen and … in Syria are the ones in charge of terrorist missions targeting France."
French investigators suspect Cherif helped Kouachi get brief training from al- Qaida in the Arabian Peninsula during the visit to Yemen. U.S. intelligence officials believe the al-Qaida offshoot also provided $20,000 to Kouachi to fund the Charlie Hebdo plot, but they say the group's involvement appears to have been limited.
Kouachi received "a general directive about going after those who insulted the prophet," said a senior US intelligence official familiar with the case. "Charlie Hebdo fits that. I have yet to see more information about hands-on management or command and control by AQAP. There was some type of engagement or meeting in Yemen, and he expressed a desire to take action. AQAP blessed it."
During his rampage in Paris, Kouachi told a journalist by phone that he had acted on the direct orders of Anwar al-Awlaki, the group's US-born ideologue, who was killed in Yemen in September 2011. But investigators have not confirmed that he actually met Awlaki, according to Thibault-Lecuivre, the prosecutors' spokeswoman.
French investigators are also looking at Benghalem's possible links to the case, officials said. They believe "an attack on US interests in France was discussed by Benghalem during the meetings with al-Qaida" in Yemen, Thibault-LeCuivre said. "But the attack didn't happen."
Like the others, Benghalem had exploited the legal system. He had racked up arrests for robbery, assault, guns and drugs by 2001, when he and an accomplice concealed guns in traditional djellabah robes and opened fire on gang rivals in a Paris housing project. One man died.
After a year on the run in Algeria, Benghalem returned and was convicted of attempted murder because evidence showed his gunshots missed the victim. Benghalem served only about half an 11-year sentence, authorities say. In prison, he radicalized under the influence of his cellmate: a Buttes-Chaumont homeboy who had lost an eye and an arm in the battle of Fallujah, French intelligence officials said.
The Charlie Hebdo case suggests that bonds formed in French streets and jails were more crucial than al-Qaida strategists, according to counterterror experts.
"These guys are not sleepers," said Marc Sageman, a former CIA officer and scholar on terrorism. "It's a homegrown, bottom-up attack. It's a far more complex story than calling it an AQAP attack."
Today, French and US intelligence officials believe Cherif remains active with al-Qaida in Yemen.
Benghalem, meanwhile, found refuge in Syria with the Islamic State, intelligence officials say. The U.S. State Department publicly designated him as a terrorist last year, alleging that he presides over executions as a member of an Islamic law panel.
The career criminal, authorities say, has become a judge.
This story was co-published with The Daily Beast.
Read more of Sebastian Rotella's coverage of international terrorism.
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