Intelligence From al-Baghdadi Raid, Including 2 Prisoners, Could Reveal Trove of ISIS Clues

Officials cautioned that the intelligence was unlikely to generate leads for quick follow-up strikes on the Islamic State.

WASHINGTON — Delta Force commandos took two Islamic State fighters as prisoners and a trove of intelligence from the now-destroyed compound where Abu Bakr al-Baghdadi, the world’s most wanted terrorist, had been hiding, officials said Monday.

The prisoners, who are being held in Iraq, are being questioned by the United States military. If the Trump administration follows its previous practice with captured Islamic State fighters, the men will eventually be turned over to the Iraqi government for prosecution.

Both the captives and the documents taken from the compound during a two-hour search of the area following the nighttime raid in which Mr. al-Baghdadi was killed over the weekend could provide a trove of information for the military and intelligence agencies, current and former officials said.

Officials said the intelligence is expected to underscore assessments that Mr. al-Baghdadi no longer exercised direct operational control over the group. Officials cautioned that the Pentagon, the C.I.A. and other intelligence agencies were still conducting a preliminary review of the confiscated documents and electronic records.

The intelligence material that commandos seized from the compound in northwest Syria where Mr. al-Baghdadi was hiding is likely to contain new details about the group’s operations.

But the officials said they did not expect to find intelligence that would quickly generate follow-up strikes on the Islamic State.

In an interview broadcast in Iraq, Mr. al-Baghdadi’s brother-in-law, Mohammad Ali Sajid, described how the Islamic State leader had communicated with messages sent on flash drives and how people around him had used cellphones. American officials have previously said that Mr. al-Baghdadi did not allow people around him to carry phones, to prevent his location from being discovered through electronic eavesdropping.

Whatever material was found by the Delta Force team, the trove of information could nonetheless shed critical light on how the Islamic State operated, including planning and financial information. The Islamic State famously kept extensive records on its brutal rule in Iraq and Syria, and some former intelligence officials suggested that Mr. al-Baghdadi might have left behind lists of deputies, couriers, contacts and other information that would be useful to American counterterrorism officials.

“ISIS was a bureaucratic organization,” Nicholas J. Rasmussen, the former director of the National Counterterrorism Center, said Monday. “Did he carry any of that stuff around? Rosters of people from other countries. Foreign fighters. Does he have all of that on a disk?”

He added, “It is all about building an understanding of the organization and how it functions.”

The two prisoners seized by Delta Force commandos were in American custody, Gen. Mark A. Milley, the chairman of the Joint Chiefs of Staff, told reporters on Monday, but he declined to give details.

General Milley described roughly how the commandos had discovered Mr. al-Baghdadi hiding in the tunnels. In the Iraqi broadcast interview, Mr. Sajid, Mr. al-Baghdadi’s brother-in-law, described how the Islamic State leader had lived in underground tunnels, equipped with a library of religious books, a ventilation system and lights. He described one of the tunnels Mr. al-Baghdadi had lived in as a bunker that was about eight yards long and about five yards wide.

In the interview with Mr. Sajid, which was broadcast by Al Arabiya Hadath, he said that when Mr. al-Baghdadi changed locations he had traveled in two white Toyota pickups accompanied by five men.

A senior State Department official said on Monday that American forces also had killed Abu Hassan al-Muhajir, the man believed to be the deputy of Mr. al-Baghdadi, over the weekend. Mr. al-Muhajir also served as a spokesman for the terrorist group, the official said. The operation took place in the area of Jarabulus near the Euphrates River, the official added, and a militia led by Syrian Kurds played a big role.

Also on Monday, General Milley spoke by telephone to his Russian counterpart, Gen. Valery Gerasimov, the chief of the Russian General Staff. The two had spoken about Syria earlier in October, as part of the efforts to de-conflict American and Russian operations in Syria. General Milley also spoke to Gen. Nicholas Carter, the United Kingdom’s Chief of Defense Staff.

Intelligence officials are expected to scour the new material for information about ties between Mr. al-Baghdadi and the Islamic State’s affiliates in other countries. That could help the American government better understand how quickly the affiliates could move in a different direction from the core Islamic State group without Mr. al-Baghdadi.

“It will also provide useful insights into the extent to which Baghdadi exerted operational control over ISIS remnants in other countries,” said Norm Roule, a former C.I.A. officer and expert on the Middle East.

Because Mr. al-Baghdadi moved around, the amount of material at the compound may have been limited. Still, even a few thumb drives, computers or other devices could provide huge amounts of data.

And Delta Force commandos who gathered the material after the raid spent two hours or so on the ground and collected a large amount of material, a person familiar with their search said.

The intelligence could also yield clues about the next leaders of the Islamic State, clarifying for intelligence agencies whether a potential successor is preparing to take over and assert control over both Islamic State fighters in Syria as well as its affiliates.

“We should be on the lookout for a personality who seeks to replace Baghdadi and create ISIS 2.0,” Mr. Roule said.

Mr. al-Baghdadi was unusual among terrorist leaders in his ability to both inspire overseas attacks as well as command them, according to intelligence officials. While he directed cells of Islamic State militants who conducted attacks in Europe, his propagandists also inspired lone gunmen in Europe and the United States to mount attacks that were much harder to detect and prevent.

During its campaign against the Islamic State in Iraq and Syria, the United States military focused less on targeting traditional leadership and more on hunting and killing the group’s best propagandists and English language translators. The campaign ultimately diminished the group’s ability to inspire attacks, military officials believed, but they are hopeful they can learn more about the impact of their strikes by analyzing the information seized from Mr. al-Baghdadi’s compound.

Fully examining the intelligence from the raid could take months, according to American officials, who compared the coming workload to the C.I.A.’s examination of the materials seized during the deadly 2011 raid on Osama bin Laden’s compound in Pakistan.

Intelligence agencies spent months reviewing that material — and senior officials said that analysts continued to examine some of it for insights on Al Qaeda.

The bin Laden intelligence yielded important details on how he ran Al Qaeda, how he communicated with the outside world and his relationships with other Qaeda leaders. American officials said they hoped for similar information from the al-Baghdadi trove.

“I might anticipate less by way of operational materials and more by way of big-picture strategic materials, such as regarding the group’s overall plans for resurgence in the future,” said Joshua A. Geltzer, a former senior director for counterterrorism on the National Security Council in the Obama administration.

The trove of material seized in Saturday’s raid could be comparable to what was seized in another Delta Force mission in eastern Syria in May 2015.

That raid on the multistory residence of Abu Sayyaf, described by American officials at the time as the Islamic State’s top financial officer, gave the American-led coalition its first big break in revealing valuable information about the group’s leadership structure, financial operations and security measures by analyzing materials.

The information harvested from the laptops, cellphones and other materials recovered from the raid — four to seven terabytes of data, according to one official — included how Mr. Baghdadi operated and sought to avoid being tracked by coalition forces.

“Capturing al-Baghdadi’s safe house means exposing data that will cause significant lasting damage to the broader terrorist network,” Ian Bremmer, the president of Eurasia Group, a research and consulting firm, said in an online newsletter on Monday.

Any more raw information from the al-Baghdadi raid is unlikely to materialize. After the Delta Force troops swept the compound and left, American warplanes and drones destroyed the compound and its tunnel network in a series of airstrikes, with the intention of keeping the site from becoming a shrine.