WASHINGTON (NYTIMES) - Four months after an Islamic State of Iraq and Syria (ISIS) suicide bomber killed scores of people, including 13 American service members, outside the airport in Kabul, Afghanistan, US and foreign intelligence officials have pieced together a profile of the assailant.
Military commanders say they are using that information to focus on an ISIS group cell that they believe was involved in the attack, including its leadership and foot soldiers.
The cell members could be among the first insurgents struck by armed MQ-9 Reaper drones flying missions over Afghanistan from a base in the Persian Gulf. The United States has not carried out any airstrikes in the country since the last American troops left Aug 30.
The attack at the airport's Abbey Gate unfolded four days earlier, during the frenzied final days of the largest non-combatant evacuation ever conducted by the US military. It was one of the deadliest attacks of the 20-year war in Afghanistan.
The ISIS group identified the suicide bomber as Abdul Rahman al-Logari. US officials said he was a former engineering student who was one of several thousand militants freed from at least two high-security prisons after the Taliban seized control of Kabul on Aug 15.
The Taliban emptied the facilities indiscriminately, releasing not only their own imprisoned members but also fighters from Islamic State Khorasan, or ISIS-K, the group's branch in Afghanistan and the Taliban's nemesis.
"It's hard to explain what the thinking was in letting out people who were a threat to the Taliban," Mr Edmund Fitton-Brown, a senior UN counterterrorism official, said at a recent security conference in Doha, Qatar.
Al-Logari was not unknown to the Americans. In 2017, the CIA tipped off Indian intelligence agents that he was plotting a suicide bombing in New Delhi, US officials said.
Indian authorities foiled the attack and turned al-Logari over to the CIA, which sent him to Afghanistan to serve time at the Parwan prison at Bagram Airfield. He remained there until he was freed amid the chaos after Kabul fell.
Eleven days later, on Aug 26 at 5.48pm, the bomber, wearing a 25-pound explosive vest under his clothing, walked up to a group of US troops who were frisking those hoping to enter Hamid Karzai International Airport.
He waited, military officials said, until just before he was about to be searched before detonating the bomb, which was unusually large for a suicide vest, killing himself and nearly 200 others.
The attack raised ISIS-K's international profile and positioned it both as a major threat to the Taliban's ability to govern the country and, according to American officials, as the most imminent terrorist risk to the United States coming out of Afghanistan.
"The group has gained some notoriety in a way that could be quite compelling for them on the transnational stage," Ms Christine Abizaid, director of the National Counter-terrorism Centre, said in October at a national security conference in Sea Island, Georgia.
"At the same time, they're fighting the Taliban. How that force-on-force engagement in Afghanistan will go will have some defining characteristics about what the transnational threat looks like."
In October, Mr Colin Kahl, under-secretary of defence for policy, told the Senate Armed Services Committee that ISIS-K could be able to attack the United States sometime in 2022. "We could see ISIS-K generate that capability in somewhere between six and 12 months," he said.
The Parwan prison at Bagram and the Pul-e-Charkhi prison near Kabul were the Afghan government's two main high-security prisons. The United States built Parwan in 2009 and transferred it to Afghan government control three years later.
On July 1, with little warning and no public ceremony, US forces abandoned Bagram Airfield, the main hub for American military operations. Six weeks later, on Aug 15, Taliban fighters swept into the base and threw open the prison gates.
The Taliban killed one prominent prisoner - a former top leader of the ISIS group in Afghanistan, Omar Khalid Khorasani - and released more than 12,000 others, including roughly 6,000 Taliban, 1,800 ISIS-K and nearly three dozen Al-Qaeda fighters, according to US officials.
"The fiasco in Afghanistan has put hundreds of terrorists back on the street," said Mr Bruce Riedel, a former CIA officer who ran President Barack Obama's first Afghanistan policy review.
One of them was al-Logari, the son of an Afghan merchant who frequently visited India and Pakistan for business. Al-Logari moved to India in 2017 to study engineering at Manav Rachna University near New Delhi.
Recruited by ISIS-K, al-Logari was arrested in relation to the New Delhi plot and handed over to the CIA by India's foreign spy service, the Research and Analysis Wing, in September 2017, according to Indian media reports that were confirmed by US and Indian officials. A CIA spokesperson declined to comment.
Al-Logari spent time in both the Pul-e-Charki and Parwan prisons, US officials said, but it is unclear how he linked up with the ISIS-K attack cell in Kabul, or why and how he came to be the Abbey Gate bomber.
Soon after the attack, however, American officials and US media reports disclosed that the bomber had been released from prison just days earlier.
The ISIS group seized on the spectacular nature of the bombing, boasting about its size, location and timing in social media posts, according to the SITE Intelligence Group, which monitors jihadi media.
In the months since the attack, US intelligence analysts and military officials say they have focused on learning more about the ISIS-K strike cell, and any future attacks it may be plotting against the West.
President Joe Biden and his top commanders have said the United States would carry out "over-the-horizon" strikes from a base in the United Arab Emirates against ISIS and Al-Qaeda insurgents who threaten the United States.
General Frank McKenzie, head of the US Central Command, said in early December that the departure of the American military and intelligence assets from Afghanistan had made tracking the groups harder but "not impossible."