Almost a year after Islamic State terrorists killed 130 people in Paris, U.S. intelligence agencies have identified one of the suspected masterminds of that plot and a follow-up attack in Brussels.

U.S. counterterror officials said the man, who goes by the name Abu Sulaiyman al Fransi (Abu Sulaiyman, the Frenchman) is a 26-year old Moroccan who once served in Afghanistan as a soldier in the French Foreign Legion. He did prison time for drug running before going to Syria in 2014 and joining ISIS, according to U.S. officials and French court documents. His real name is Abdelilah Himich, according to U.S. counterterror officials.

Watch the Film “Terror in Europe” premiered Tuesday, Oct. 18. Watch it online. See the Series A look at how the region is grappling with terrorism attacks — and how revolving-door prisons could be compounding the threat. See our reporting.

Despite his relative youth, Himich’s military experience and knowledge of France have made him a key figure in the Islamic State’s external operations unit, which has led a terror campaign against Europe, officials said. He is thought to be in Syria.

“We believe he is one of the top guys involved in spearheading the Paris attack and the Brussels attacks,” a U.S. counterterror official said. “He was involved in creating that infrastructure” of the external operations unit.

U.S. and European counterterror officials were interviewed for this story as part of a report by ProPublica and Frontline about terrorism in Europe.

Officials acknowledged that they have struggled to pin down details about the identities and activities of the ISIS planners. U.S. and European counterterror officials note that several Islamic State fighters have used the nom de guerre Abu Sulaiyman al Fransi. (The nickname is spelled in a number of ways, U.S. officials say.) In the past, he has variously been described by European officials and media reports as a blond convert and a former physical education teacher.

But U.S. officials said there was strong evidence indicating that the senior French fighter in question is Himich. They said French intelligence has been informed of that assessment and agrees with it.

European counterterror officials interviewed by ProPublica earlier this year said they also suspect that a militant known as Abu Sulaiyman the Frenchman helped to plan the Paris and Brussels attacks. But they did not disclose his full identity.

Officials said that months of investigations and intelligence work in Europe and the Middle East have begun to shed light on the command structure of what the Islamic State calls external operations. The predominantly Arab leaders of ISIS have given senior and mid-level European fighters considerable autonomy to select targets and decide details of plots in their home turf, according to Western counterterror officials.

Nonetheless, the ISIS unit that plots attacks overseas is also quite bureaucratized, according to U.S. intelligence officials. The unit exerted increasingly direct control over plots in Europe starting in 2015, according to Western counterterror officials, and is part of an ISIS intelligence structure known as the Enmi.

“ISIS-directed plots in Europe have usually involved several planners and organizers who might change for each project,” said Jean-Charles Brisard, the chairman of the Center for the Analysis of Terrorism in Paris, who has been studying the unit. “It’s more a team process than a single mastermind’s plan.”

Abu Mohamed al-Adnani, a Syrian who served as a spokesman for the Islamic State, was a top figure overseeing external operations, counterterror officials say. A U.S. drone strike killed Adnani in August.

There is hard evidence that another ISIS militant in Syria, a man known as Abu Ahmad, played a hands-on role in the Paris and Brussels cases, according to European counterterror officials. A laptop computer recovered by Belgian police after the Brussels bombings in March contained encrypted communications detailing Abu Ahmad’s direct role in the plot.

During the four months after the Paris attacks, Abu Ahmad discussed targets, strategy and bomb-making techniques from Syria via encrypted channels with survivors of the terrorist cell who were hiding in Brussels. The fugitive suspects referred to Abu Ahmad as their “emir,” or leader, according to Belgian counterterror officials.

The communications in the laptop indicate that the original plan was to hit France again, European officials say. When Belgian police closed in, however, Abu Ahmad told the fugitives to strike in Brussels instead, officials said. The suicide bombings killed 32 people at the airport and a subway station on March 22.

Abu Ahmad was described by two captured ISIS fighters as a lead planner of the Paris massacre as well. The suspects, an Algerian and a Pakistani, told interrogators that Abu Ahmad chose and prepared them for the plot last fall, and sent them to Europe posing as Syrian refugees, according to European counterterror officials.

When the two landed in Greece in October, however, Greek border guards discovered they were not Syrian, and held them for a few weeks, according to European and U.S. counterterror officials. After being released, the duo communicated with Abu Ahmad, who sent them money and instructions not to join the rest of the attackers, according to officials. The two suspects were arrested in Austria in December.

The men described Abu Ahmad as a Syrian, according to European counterterror officials. But the recovered clandestine communications with the plotters in Europe indicate clearly that he speaks French, raising questions about his true nationality, the officials said.

“He has to be French, or speak French well,” a European counterterror official said. “They use French slang.”

The investigation shows that Abu Ahmad worked with the senior fighter known as Abu Sulaiyman al Fransi, according to European and U.S. counterterror officials. During the massacre at the Bataclan concert hall in Paris, witnesses overheard gunmen talk to each other about calling a person named Abu Sulaiyman, according to European and U.S. officials.

Himich, the man identified by U.S. intelligence as Abu Sulaiyman, has an unusual story. He was born in Rabat, Morocco, in 1989, according to U.S. counterterror officials and French court documents. His family emigrated when he was an adolescent to Lunel, a southern French town about 20 miles from Montpellier, officials say.

Lunel has a population of about 25,000 and a rich history as a Jewish cultural center in medieval times. The town has a large population of Muslim descent as the result of immigration from North Africa beginning in the 1960s.

In 2006, Himich’s name appeared in a Lunel high school newspaper as the author of an article about teenage drinking. Although he went to school in France, he remains a Moroccan citizen, according to officials and court documents. In 2008, he joined the French Foreign Legion, a legendary and hard-nosed force whose soldiers come from all over the world

Himich “distinguished himself during various missions in Afghanistan,” according to the court documents. In 2010, however, he deserted, according to the officials and documents.

“Wanting to attend the burial of his father, he left his post without authorization,” the documents say. “After his return to France, he did vocational training to work in the security field and also considered becoming a nurse.”

A year later, he got in trouble with the law. French customs police intercepted him arriving on a train from Amsterdam at the Gare du Nord station in Paris on Dec. 13, 2011, according to court documents. Police discovered he was carrying a backpack containing 2.6 pounds of cocaine with a street value of about $55,000. He also tested positive for cocaine and marijuana.

Himich testified that he had met a Senegalese man at a hookah bar in Paris, and told him he needed money because he had left the Foreign Legion. Himich said the man hired him to bring a package from Rotterdam, offering to pay $1,600. Himich, whom the documents describe as “adopting an arrogant attitude” during a court hearing, denied knowing that the package contained drugs.

Himich spent five months in jail. He was convicted in April 2013, and sentenced to three years in prison with a year suspended, according to the documents, though it appears he did not spend much more time behind bars. It was his first criminal conviction. He appears to have followed a classic trajectory from crime into radicalization.

Despite its picturesque setting, Lunel has made headlines as a hub of extremism. By 2015, at least two dozen young people — of North African descent as well as Muslim converts — had left Lunel to fight in Syria, where at least six of them died.

Himich joined that exodus in early 2014, according to U.S. counterterror officials. He rented a car and drove via Italy, Greece and Turkey to Syria, according to Brisard. That route is popular with Syria-bound jihadis who travel with their families, according to Italian police. Himich has a wife and two children, officials said.

In Syria, Himich first fought in an al-Qaida-linked group, officials say. Then, like many extremists in Syria, he moved to the increasingly powerful Islamic State. He soon became a battlefield commander, according to U.S. officials and Brisard, the French counterterror expert.

“He was quickly promoted by ISIS to lead one of its fighting brigades in the first half of 2014,” Brisard said. “His rapid rise within ISIS could be explained by his military service in the French Foreign Legion.”

France and Interpol have issued warrants for Himich’s arrest on suspicion of terrorist activity, according to U.S. officials.

Investigators believe Himich is among a group of ISIS militants in their 20s and 30s, predominantly Francophones, who plot against Europe. The group also includes two Muslim convert brothers from Toulouse, Fabien and Jean-Michel Clain, according to counterterror officials. Fabien Clain is believed to be the Frenchman who read the official statement in which the Islamic State claimed responsibility for the Paris attacks, officials say.

The Clain brothers surfaced in an investigation in 2009 of a French-Belgian extremist network. Suspects in that case had been investigated for a bombing in Cairo and, according to investigators, told Egyptian interrogators they had discussed a potential attack on the Bataclan, the nightclub that was hit in 2015. The suspects allegedly saw the Paris concert hall as a Jewish target because the owners were Jewish and the venue had hosted pro-Israel events.

Given his military experience, Himich’s stature is likely to grow after the recent deaths of Islamic State leaders in U.S. air strikes, officials said.

“He’s probably one of the most important Frenchmen in ISIS, especially after the death of Adnani,” the U.S. counterterror official said.