In the hours before the coordinated attacks in Paris two years ago, a 10-man unit of Isis fighters carpooled to the city, where they shared hotel rooms before strapping on suicide belts.

Weeks later, Isis released a video eulogising them as “lions,” and sharing clips of each fighter pledging allegiance to the militant group.

Each fighter, that is, except Salah Abdeslam, the only member who did not die in the attacks, and who instead went on the run. He was dragged from his hideout in Belgium following a months-long manhunt.

To date, analysts say, he has said little to interrogators who have pressed him for details on how the cell hatched its plan, the worst terrorist attack in French history.

His absence from the numerous releases distributed by the group — which often included photographs of his older brother, who detonated his belt in a Parisian cafe on the night of the attacks — pointed to what would become a trend.

It may help explain why Isis had not, as of Thursday afternoon, asserted responsibility for the deadly rampage the day before in Manhattan by a truck driver who was wounded and arrested by the police, who say he is a disciple of the group.

With few exceptions, Isis has not claimed attacks when a surviving recruit falls into the hands of the authorities.

“It’s as if he didn’t even exist,” said Jean-Charles Brisard, director of the Center for the Analysis of Terrorism in Paris, regarding the omission of the 10th attacker from the group’s propaganda.

Isis has followed this practice regardless of whether the attacker was directly dispatched or inspired remotely through online tutorials.

Among the attacks that investigators have definitively tied to the group — and which it never claimed, despite the casualties they caused — were those at the Jewish Museum in Brussels in 2014, which left four dead, and on the Thalys train in 2015, which wounded three.

Last year, when Ahmad Khan Rahimi, who planted bombs in New Jersey and in Manhattan’s Chelsea neighbourhood, was finally taken into custody, police also found his bloodstained journal, containing references to Abu Muhammad al-Adnani, Isis spokesman and the leading figure calling for attacks on the West. But Isis did not take responsibility for Rahimi’s acts.

More recently, Isis never claimed a truck-ramming in Stockholm in April, even though the perpetrator was found to have been a recruiter for the group.

Nor did the group take responsibility for a vehicular attack in Edmonton, Canada, just over a month ago, carried out by a man who took the time to drape the Isis flag on the dashboard of his Chevrolet Malibu before using it to ram through a traffic barricade.

The constant in each of these cases is that the perpetrator was apprehended.

More than 24 hours after the arrest of the driver in the Manhattan assault, which left eight people dead, the group’s media arm remained mum, even though he had left a note stating that the “Isis will endure forever,” a reference to the group’s slogan.

The lack of a claim is conspicuous in light of how much territory the group has lost in Syria and Iraq in recent months, erasing 90 percent of the caliphate it once held. Claiming responsibility for the truck rampage in New York, the worst terrorist attack in the city since 11 September 2001, might be expected to project an image of strength for the group.

A New York Times tally of the more than four dozen attacks on Western targets claimed by the group since 2014 indicates that the Isis typically issues its claim of responsibility within 24 hours, though there have been some exceptions, including two attacks this past summer that the group claimed a month later.

It is possible that the group is simply taking its time.

Among the arguments for why Isis would not claim responsibility, even when everything points to it, is a pragmatic consideration.

“It’s essentially about loyalty. No one would be motivated to do an Isis attack if they know that when they end up getting caught, someone will out them,” said Raphael Gluck, an independent researcher who focuses on the group’s digital footprint and has embedded himself in many of the group’s online chat rooms. “It would work counter to their whole recruitment line and would serve to push off the next attack.”

Amarnath Amarasingam, a senior research fellow at the Institute for Strategic Dialogue, who has interviewed Isis followers online as part of his work, said that members of the group explained to him that not asserting responsibility for attacks was intended to protect fighters.

“I think it’s very much a matter of internal communication,” he said, “a way of telling their supporters that if they are captured, they won’t be sold out by the group.”

Others said they see a theological justification: The Isis encourages recruits to die in a standoff with police in a “martyrdom operation.” When the fighter survives, the mission is incomplete, Brisard said.

This theory has been given weight by several recent attacks, including the London Bridge and the Barcelona attacks this summer, in which assailants wore what turned out to be fake suicide belts. Online tutorials teach followers how to make these look-alike vests, strapped on for the purpose of inviting law enforcement’s gunfire.

New York Truck attack Show all 6 1 /6 New York Truck attack New York Truck attack Investigators inspect the truck following the attack Investigators inspect a truck following a shooting incident in New York on 31 October 2017. Several people were killed and numerous others injured in New York on Tuesday when a suspect plowed a vehicle into a bike and pedestrian path in Lower Manhattan, and struck another vehicle on Halloween, police said. A suspect exited the vehicle holding up fake guns, before being shot by police and taken into custody, officers said. The motive was not immediately apparent. Getty New York Truck attack A paramedic looks at a body along the bike path A paramedic looks at a body covered under a white sheet along the bike path 31 October 2017, in New York. A motorist drove onto a busy bicycle path near the World Trade Center memorial and struck several people Tuesday, police and witnesses said. AP Photo/Bebeto Matthews New York Truck attack The truck driver collided with a school bus Authorities respond near a damaged school bus Tuesday, 31 October 2017, in New York. A motorist drove onto a busy bicycle path near the World Trade Center memorial and struck several people, police and witnesses said. Two adults and two children were on the bus at the time. AP Photo/Bebeto Matthews New York Truck attack A young girl reacts to the scene A young girl reacts as police officers secure an area following a shooting incident in New York on 31 October 2017. Several people were killed and numerous others injured in New York on Tuesday after a vehicle plowed into a pedestrian and bike path in Lower Manhattan, police said. 'The vehicle struck multiple people on the path,' police tweeted. 'The vehicle continued south striking another vehicle. The suspect exited the vehicle displaying imitation firearms & was shot by NYPD.' DON EMMERT/AFP/Getty Images New York Truck attack Police officers arrive at the scene Police officers arrive at the scene following a shooting incident in New York on 31 October 2017. Multiple people were hurt in downtown Manhattan, US media reported after police confirmed that they were responding to reports of a shooting. Police said they had mobilized to the scene in Lower Manhattan and that one person was in custody, giving no further details. DON EMMERT/AFP/Getty Images New York Truck attack Emergency personnel respond to truck attack in lower Manhattan Emergency personal respond after reports of multiple people hit by a truck after it plowed through a bike path in lower Manhattan on 31 October 2017 in New York City. According to reports up to six people may have been killed. Kena Betancur/Getty Images

That motivation may also explain why the Manhattan assailant, Sayfullo Saipov, emerged from his rented Home Depot truck armed with both a pellet gun and a paintball gun, neither powerful enough to cause significant harm, but making him look dangerous to the police.

“According to their logic, their ideology, they are supposed to die during the action,” Brisard said.