>> tonight, with a wave of new attacks in the ufrontline and propublica's investigation of how isis and al qaeda brought terror to mainland europe. >> here you have a convicted terrorist who's able to leave the country, go to a terrorist haven, without being detected. how is that possible? >> propublica reporter sebastn rotella uncovers a trail of evidence across france, belgium, and spain... >> these individuals were on the radar. >> ...revealing what europe's top counterterror officials knew... >> (translated) the question everyone had was not if something would happen, but rather when and where. >> ...what they missed... >> (translated): the judges did

not realize that these people were time bombs. >> ...and why europe remains so vulnerable. >> there's every reason to expect that we'll see isis lash out while it's under pressure in syria and iraq to maintain its relevance. >> tonight ofrontline, "terror in europe." >> frontlinis made possible by contributions to your pbs station from viewers like you. thank you. and by the corporation for public broadcasting. major support for frontliis provided by the john d. and catherine t. macarthur foundation, committed to building a more just, verdant, and peaceful world. more information is available at macfound.org. additional support is provided by ford foundation, working with visionaries on the front lines of social change worldwide, at fordfoundation.org. the park foundation, dedicated to heightening public awareness of critical issues. the john and helen glessner family trust, supporting trustworthy journalism that informs and inspires.

and by the frontline journalism fund, with major support from jon and jo ann hagler, and additional support from joseph azrack and abigail congdon. >> (translated): for many years, terrorism was something hypothetical, something that happened elsewhere. but at a certain point, you have to open your eyes. how did we not see this coming? >> narrator: in early 2015, belgian police, with the help of u.s. and french intelligence, were preparing to launch a raid on a terrorist cell thought to

be on the verge of an attack. the suspects were hiding out in the town of verviers. (speaking french) >> (translated): they were clearly in contact with people who could have turned them in. but nobody did. these people were extremely careful, they never left the apartment. we knew we would face determined men. they had weapons, they had explosives. (gunfire) >> narrator: when belgian commandos stormed the hideout, they came under heavy fire. (shouting and gunfire) they shot two men dead and wounded another. investigators found explosives, fake ids, and police uniforms.

>> (translated): we discovered they had connections to syria, to isis. we quickly realized this was the start of a campaign across europe. we thought this could be the beginning of a new era. unfortunately, we were right. >> narrator: since january 2015, an unprecedented wave of terror attacks has overwhelmed europe's defenses. (gunfire) (man shouting) that month, attacks against charlie hebdo magazine and a jewish supermarket in paris left 17 people dead. (gunfire) on november 13th in paris, isis attacked multiple targets, killing 130 people.

four months later... suicide bombings killed 32 in brussels. propublireporter sebastian rotella has been covering terrorism for two decades. years before the attacks, he was already reporting on some of the jihadists who would go on to strike europe, and the counterterror officials trying to stop them. in this film, he sits down with the men and women on the inside of the fight against al qaeda and isis. they reveal the missteps and systemic breakdowns that allowed known terrorists to hit the heart of europe, how the problems persist today, and the unprecedented threat the continent faces. >> (translated): it's a disaster. why were they not monitored and stopped?

these people were time bombs. >> these individuals were on the radar, they had traveled to syria, they were known to law enforcement intelligence officials. >> no system is perfect. and we live in a free world. how much of your freedom do you want to sacrifice for your security? (gunfire, explosion) >> (translated): the november 13th attacks should never have happened. the brusslls attacks should never have happened. the system has completely failed.

>> narrator: in 2003, french intelligence began monitoring a group of islamic radicals who lived near the buttes-chaumont park in northeast paris. they were young, untrained and inexperienced. but one member of this gang would ultimately carry out the charlie hebdo attacks, 12 years later. cherif kouachi was a petty criminal and aspiring rapper. the son of algerian immigrants, he'd grown up in an orphanage after his parents died. when he was 21, kouachi was radicalized by the u.s. invasion of iraq and joined the extremists of the buttes- chaumont gang. they were plotting to go to iraq and kill americans. >> (translated): it was a small group of people, young men, not particularly religious.

most of them criminals, drug dealers, robbers. they were seduced by talk of supporting the muslim community. >> narrator: louis caprioli was then the counterterror chief of french domestic intelligence. rotella first met him while reporting on the buttes-chaumont gang. >> (translated): french domestic intelligence and the police were watching that group. in january 2005, the authorities began to dismantle the network. cherif kouachi was arrested as he was about to board a plane to go to iraq and fight. >> narrator: kouachi was sent to fleury-mérogis prison to await trial. while he was locked up, his extremist connections only deepened.

the prison was a hotbed of jihadism dominated by al qaeda veterans. kouachi became friends with another radicalized criminal who would ultimately join him in his terrorist project: amedy coulibaly. >> (translated): they could communicate with each other. it was totally porous. it was disturbingly easy to form connections. so they expanded their network and became worse than when they arrived in prison. >> narrator: marc trévidic was a top counterterror prosecutor and judge who investigated kouachi's network. he says the french judicial system was not set up to deal with the long-term threat they posed. >> (translated): that was our tragedy, in a way. we thought that if there are no attacks on french soil, then the anti-terrorist system is working correctly, therefore everything is fine. in fact, nothing was fine. these may have been terrorists

linked to al qaeda, but they were seen as people who were leaving the country to fight. so they weren't seen as a direct threat against us. >> narrator: as the gang had not carried out an actual attack, french law dictated that they be tried in a low-level court alongside robbers and drug dealers, where the maximum sentence was only ten years. in 2008, kouachi was convicted of recruiting fighters to go to iraq and attempting to join al qaeda. his sentence was three years, with 18 months suspended. >> the contrast between the way european nations deal with terrorism from a criminal perspective and the united states is quite stark. >> narrator: matt olsen led the u.s. national counterterrorism center between 2011 and 2014; before that he was a prosecutor and the nsa's chief lawyer. >> rotella: what would the sentence be for somebody like that in the u.s.? >> hypothetically, someone like kouachi with that charge would

be looking at far in excess of 15 years, the conspiracy to provide support to a terrorism group. and the important thing there is that 15 years, for somebody who's in their mid-20s or their 30s, you know, that brings them the hope is that by the timend they're released, they're not interested or too old to really be involved. >> narrator: kouachi wasn't alone. amedy coulibaly rved only three years for his involvement in a plot to help a convicted terrorist escape from prison. no one else in the buttes- chaumont crew served more than seven years, even dangerous fighters who saw combat in iraq. today several are active terrorists. >> (translated): the judges did not realize that these people were time bombs. they didn't rightly assess their truly dangerous nature. consequently, they were given light sentences, perhaps to try to reintegrate them into

society. >> (translated): we were mistaken in our assessment of quite a lot of people who we thought were less dangerous than they actually were. from the moment they stepped out of prison they left with an even greater hatred towards france than before. we only increased their wish for revenge and their determination to hurt us. >> narrator: having already spent 20 months in prison awaiting his trial, kouachi left court a free man. by this time, louis caprioli had retired. >> rotella: for a police officer like you, who has worked to put these people in jail, how does that make you feel? >> (translated): it is a feeling of failure.

a feeling of failure as we are perfectly aware that these people have not been removed from the action, and that they will come back even more dangerous. >> narrator: in the years following his release, kouachi was investigated again for suspected terrorist activity, but never convicted. in 2011, he took advantage of a fatal flaw in europe's counterterror defenses: weak border control. concealing his identity by using his brother's passport, he left france and traveled to yemen to join al qaeda. >> rotella: here you have a convicted terrorist who is able to leave the country, go to a dangerous part of the world, a terrorist haven, without being detected. how's that possible? >> well, absolutely, so somebody should not be able to cross international borders who's been convicted of a terrorism offense and who's seeking to travel to a

place like yemen. here in the united states after 9/11, we established a single watch list for known or suspected terrorists-- the no-fly list. in europe, there's not one single watch list for europe. they have not developed a way to effectively stop somebody from traveling, even though in this case, the individual was convicted of terrorist offenses. >> narrator: for more than a decade, counterterror chiefs have proposed laws to improve border defenses, such as giving european security forces systematic access to data that airlines collect about all passengers on the continent. u.s. border guards have used this tool, known as passenger name record, or pnr, for 15 years. but european politicians, concerned about privacy and data protection, repeatedly rejected pnr legislation. >> madam president of the council, read my lips: data protection directive. >> we have, you know, maybe a

different privacy mindset in certain countries in europe compared to the u.s. it depends on the different cultural historical political backgrounds of each country, and they are different. >> narrator: rob wainwright is the director of europol, the agency tasked with coordinating law enforcement across the 28 countries of the european union. >> the privacy-security trade- off still goes back, i think, to the legacy from the second world war where, you know, german and austrian citizens are concerned about never again shall we arrive at a position where the state can have so much authority that they can collect unlimited amounts of personal data about their citizens. and for good reason, actually. >> narrator: but, counter-terror chiefs say despite the concerns, pnr would help them intercept suspected terrorists. >> (translated): european legislators have rejected passenger name record. why? because they see it is a violation of liberties. that is a mistake. it's a flaw of our monitoring system, the way people can circulate in and out of europe.

>> narrator: in yemen, cherif kouachi met up with an old friend from the buttes-chaumont gang. peter cherif had himself absconded from france while on trial for terrorism charges and was now a fighter for al qaeda in the arabian peninsula, which was being monitored intensively by the u.s. >> the meeting that occurs in the summer of 2011, that's sort of the worst nightmare for intelligence services. because any time that al qaeda had access to someone from a western european country like france, they would try to operationalize that person, that person could give them insights about western culture, help them develop plans to carry out attacks. >> narrator: peter cherif arranged for al qaeda to give kouachi terror training and money-- $20,000, according to u.s. intelligence.

a plot began to take shape. >> (translated): during that time, they come up with the idea of avenging the prophet muhammad and of attacking people who publish caricatures of the prophet. and specifically in france, charlie hebdo. >> narrator: after three weeks in yemen, cherif kouachi returned to france undetected. he and his brother said now became an al qaeda sleeper cell. u.s. intelligence learned that one of the kouachis had visited yemen, and alerted the french, who started monitoring them. but they discovered nothing of the charlie hebdo plot. surveillance resources were already stretched, and the number of european extremists was about to surge. (explosion)

>> narrator: in 2012, the war in syria dramatically changed the european security landscape. (shouting) it spawned a new jihadist movement, isis, which set out to be even more brutal than al qaeda. in 2014, the group formally split from al qaeda and declared a caliphate, or islamic state, and summoned all muslims to join them. (speaking spanish) >> (translated): and the effect of that call is brutal. it's... well, extraordinary. our investigations multiplied

extraordinarily. >> narrator: dolores delgado is the chief counterterror prosecutor of spain's high court. as spain's liaison to france and belgium, she worked closely with her european counterparts to monitor the exploding numbers of isis recruits. >> (translated): there was a call for young people, a call for women, a call for children, and it's not to travel to the sahel, or waziristan. it's to go to syria. and syria is right next door. going to syria is very cheap. and it's very easy. >> narrator: thousands of young european muslims joined up. unlike recruits to al qaeda, aspiring isis militants often knew little about islam. >> (translated): it was open bar: anyone who wanted to join the islamic state could do so.

it was well known that al qaeda had created filters; you had to show you were trustworthy, there were a series of tests and an apprenticeship. it was not all that easy. in this case, anyone can join. even crazy people, very violent people, petty criminals. i even saw young people who were not yet radicalized going to syria. it was just a trend, a need to have fun and escape their boring lives. i'd never experienced anything like it before. >> narrator: one country, belgium, provided more isis militants for its size than any other in europe. among them was a petty criminal named abdelhamid abaaoud. the son of a shopkeeper from brussels, abaaoud had spent time in prison for assault and minor crimes. as isis was emerging in syria,

abaaoud began to draw on his criminal network to recruit volunteers to the cause. >> (translated): abaaoud had a particular profile, which allowed him to recruit a whole network that obeyed him. >> narrator: alain grignard is a senior counterterror officer with the belgian federal police, an expert in islamic extremism who speaks fluent arabic. his agency started tracking abaaoud's network in 2013. >> (translated): i think these ui