WASHINGTON — Bilal al-Sudani was no stranger to American counterterrorism officials.

Before joining the Islamic State affiliate in Somalia, Mr. al-Sudani was subjected to punitive sanctions by the U.S. Treasury Department in 2012 for his involvement with Al Shabab, Al Qaeda’s branch in the East African country.

But it wasn’t until American officials started digging deeper into the background of another Islamic State branch, the one in Afghanistan that had carried out the deadly bombing at Kabul’s international airport in August 2021, that analysts fully realized Mr. al-Sudani oversaw a sprawling ISIS financial and logistical network across Africa, Europe and Afghanistan.

Mr. al-Sudani’s newly revealed role as the financier for the ISIS branch responsible for the death of 13 U.S. service members in Kabul rocketed him to the top ranks of U.S. counterterrorism kill-or-capture lists, senior American officials said. Last week, commandos from the Navy’s SEAL Team 6 killed him in an early-morning helicopter-to-ground raid in a remote cave complex in northern Somalia.

“Al-Sudani helped to put money in the pockets of the same elements of ISIS-K responsible for Abbey Gate,” said a senior U.S. official, referring to ISIS-Khorasan and the Kabul airport location of the bombing.

The death of Mr. al-Sudani, whose Somalia-based headquarters coordinated trainers and funding for Islamic State affiliates in Afghanistan, the Democratic Republic of Congo, Mozambique and South Africa, underscores the group’s global connections and support structure, analysts say.

Despite his killing, analysts point to ISIS’ resiliency nearly four years since the end of its so-called caliphate, or religious state, in Iraq and Syria as it leverages terrorist networks to sustain new and established affiliates.

“Sudani’s death may temporarily disrupt this administrative network and the support reaching these affiliates, but is unlikely to dampen this support permanently,” the American Enterprise Institute’s Critical Threats Project said in an assessment this week.

Under intense military pressure by the United States and its local allies, the Islamic State’s leadership in Iraq and Syria has faced significant resource constraints in recent years, a sharp decline from the group’s peak as one of the best-financed terrorist organizations in the world.

This led the Islamic State to direct its affiliates to pursue financial self-sufficiency, as several “offices” coordinate revenue generation and money laundering between affiliates and networks within regions, rather than money flowing from Iraq and Syria to branches around the world, according to a recent analysis in the Long War Journal, a website run by the Foundation for Defense of Democracies that tracks military strikes against militant groups.

ISIS has attempted to expand its influence in Africa through large-scale operations in areas where government control is limited. In announcing sanctions against four South African-based financiers for the group, the Treasury Department said last March that ISIS branches in Africa were relying on local fund-raising schemes such as theft, extortion and kidnapping for ransom, as well as financial support from the ISIS hierarchy.

Somalia is better known as a sanctuary for Al Shabab, the terrorist group linked to Al Qaeda, than for the Islamic State. But the ISIS branch in the country has played an outsized role for the global terrorist organization despite having only 200 to 280 fighters.

The Islamic State’s Somalia wing includes a regional office called Al Karrar, which serves as a coordination hub for operations in the Democratic Republic of Congo, Mozambique, South Africa and the networks between them, Caleb Weiss and Ryan O’Farrell wrote in the Long War Journal analysis.

With counterparts in West Africa, South Asia, Syria and elsewhere, the Al Karrar office oversees substantial fund-raising operations through extortion rackets and criminal activity in Somalia and South Africa, the analysis concluded.

But U.S. and other Western intelligence services have in the past year detected increasing ties between Al Karrar and ISIS Khorasan in Afghanistan. A United Nations report last July concluded that Al Karrar facilitated the flow of money to the Afghan affiliate through cells in Yemen, Kenya and Britain.

The U.N. report said that ISIS Khorasan “uses these funds in the acquisition of weapons and to pay the salaries of fighters.”

Before his death, Mr. al-Sudani was thought to play a key role in, or even direct, the Al Karrar office, officials said. “There’s evidence he was pulling the strings from East Africa,” said Heather Nicell, an Africa analyst with Janes, the London-based defense intelligence firm.

One senior administration official said that no one else in the Islamic State rivaled Mr. al-Sudani in his ability to receive and distribute illicit funds — as much as hundreds of thousands of dollars at any given time — to far-flung ISIS affiliates on at least three continents through a network of clandestine contacts he had built over more than a decade.

As Mr. al-Sudani’s role in supporting ISIS fighters in Afghanistan — including the Kabul airport bomber — came into sharper focus, the military’s secretive Joint Special Operations Command ramped up its planning to kill or capture him, officials said.

The Special Operations raid on Jan. 25 took place in a remote mountainous cave complex in the Puntland region of northern Somalia, months after American spy networks first detected Mr. al-Sudani’s hidden headquarters and began using spy satellites and other surveillance aircraft to study his movements.

The American commandos had been prepared to capture Mr. al-Sudani, but he and 10 other Sudanese associates were killed in a gun battle after they resisted, a senior administration official told reporters after the raid was disclosed.

A model for these kinds of operations took place in May 2015, when two dozen Delta Force commandos entered Syria aboard Black Hawk helicopters and V-22 Ospreys from Iraq and killed Abu Sayyaf, whom American officials described as the Islamic State’s “emir of oil and gas.”

The information harvested from the laptops, cellphones and other materials recovered in that raid yielded the first important insights about the Islamic State’s leadership structure, financial operations and security measures.

The fact that the Pentagon sent commandos to kill or capture Mr. al-Sudani — a decision that required President Biden’s approval — rather than using a less risky drone operation indicated his significance.

In another sign of Mr. al-Sudani’s importance, the commandos rehearsed their secret mission at an undisclosed location in the region with similar terrain. The Navy SEAL Team 6 forces that killed Osama bin Laden in 2011 in Pakistan had practiced their mission on a mock-up of the bin Laden compound in much the same way.

For the raid against Mr. al-Sudani’s hide-out, American officials said about two dozen members of SEAL Team 6 flew in Army MH-47 Chinook helicopters, operated by the 160th Special Operations Aviation Regiment, known as the Night Stalkers, from a small, unassuming Navy vessel sailing off the Somali coast.

The commandos landed some distance from the cave complex to avoid detection, and made their way by foot to Mr. al-Sudani’s cave complex. There, an hourlong firefight ensued with Mr. al-Sudani and his associates holed up in the caves until they were killed, officials said.

A senior U.S. military official said the commandos recovered a trove of material — including laptop computers and hard drives, cellphones and other information — from Mr. al-Sudani’s hide-out that could provide tips for future counterterrorism operations.