U.S. military and intelligence officials are wary of writing off the Islamic State in Iraq and Syria despite a series of setbacks that has seen the terror group lose fighters, senior leaders and yet another would-be caliph.
The assessment comes less than a week after the Islamic State group, also known as IS, ISIS, or Daesh, announced Thursday the death of Abu al-Hussein al-Husseini al-Qurashi, who had led the terror organization since last November.
It also comes as there is some confusion about how Abu al-Hussein met his end.
Turkey initially said it killed him during an operation in late April, though .
IS, which is thought to have delayed the announcement, blamed al-Qaida-linked Hayat Tahrir al-Sham, or HTS, which promptly rejected the accusation.
Either scenario could be seen as an indication that IS' staying power is waning. But U.S. officials caution that drawing such a conclusion would be premature.
IS "is a long-term threat," a U.S. military official said, adding the U.S. was aware of the change in leadership before the terror group made the announcement on one of its Telegram social media channels.
The official, who agreed to speak only on the condition of anonymity, did not refute other assessments pointing to the terror group's overall weakness in Iraq and Syria, including U.S. estimates that put the number of IS fighters in what was once its core territory at less than 2,000.
Instead, the official said the group remains resilient, warning that its followers, including many of the estimated 10,000 fighters held in prisons across northeastern Syria, have not lost their fervor.
"If you look at these detention facilities in Syria, guarded by the [U.S.-backed] Syrian Democratic Forces, they are the single greatest concentration of terrorists on the face of the earth," the official said, noting one prison in Hasaka holds 5,000 former IS fighters alone.
One well-coordinated prison break, the official said, "can quickly rebuild ISIS ranks."
U.S. officials argue such fears are not far-fetched, pointing to a weeklong assault by nearly 300 IS fighters on the al-Sina'a prison in Hasaka in January 2022.
It was put down only after the Syrian Democratic Forces called in about 10,000 troops and with help from U.S. and anti-IS coalition fighter jets, attack helicopters and armored vehicles.
"They still aspire to conduct prison breakouts where their ISIS prisoners are held," Major General Matthew McFarlane, the commander of the U.S.-led Combined Joint Task Force — Operation Inherent Resolve, told reporters ahead of talks between U.S. and Iraqi defense officials this week at the Pentagon.
"Their ideology remains unconstrained and is still a threat as they seek to rebuild some capacity and capability to conduct attacks and to regain or reemerge as a significant threat to the population," he said.
U.S. military officials have also raised repeated concerns about large displaced-persons camps, like al-Hol in northeastern Syria, which still holds nearly 49,000 people, half of whom are children.
"About 50% of the camp holds, espouses some form of [IS] ideology," U.S. Central Command's General Michael "Erik" Kurilla told lawmakers this past March.
Other countries are equally concerned about IS' resilience, with some warning that IS in Iraq and Syria is stronger than what U.S. intelligence estimates indicate.
Intelligence shared by United Nations member states for a report published late last month suggests IS boasts between 5,000 to 7,000 followers under its command, "most of whom are fighters."
And while the tempo of IS attacks has lessened, the report found in Syria, "Small cells undertook regular attacks, including in north Palmyra and eastern Hama," and that IS "continued to use the north-east to rebuild, recruit, and try to release key leaders from prisons."
Separately, U.S. partner forces in Syria said in a U.S. Defense Department Inspector General report, released earlier this month, that IS "was actively preparing financing and training cells to conduct more attacks in Iraq and Syria."
A key question, then, for the U.S. and its allies, is how quickly and effectively IS can take advantage of a still fervent following in Iraq and Syria in order to reemerge as a major threat.
Current and former U.S. and Western intelligence officials think that will still take time.
The U.S. Defense Intelligence Agency recently said it believes IS' plans to break thousands of fighters out of prison are, at best, still aspirational, and that the terror group's overall capabilities have been significantly degraded.