A founding member and chief spokesman for Islamic State, Abu Mohammed al Adnani, was killed on a battlefield in northern Syria, the militant group said.

Adnani played an important role in Islamic State’s external operations, grooming Abdelhamid Abaaoud during his time fighting with the group in Syria before Abaaoud went on to become the ringleader of the terror attack in Paris that killed more than 100 people.

The Pentagon said Adnani was targeted in a “precision strike” in Aleppo province’s al Bab but couldn’t confirm whether he was killed.

“We are still assessing the results of the strike, but al Adnani’s removal from the battlefield would mark another significant blow to ISIL,” said Pentagon press secretary Peter Cook, using another name for the extremist group.

Adnani was considered by American defense officials as one of Islamic State’s most senior leaders, directly involved in both the recruitment of foreign fighters as well as the “chief of external operations,” according to a senior defense official. The Pentagon said he was connected to attacks that killed more than 1,800 people and wounded nearly 4,000.

Adnani was known for lengthy speeches promoting Islamic State,conveying messages from leader Abu Bakr al-Baghdadi. He would issue messages online lambasting jihadist rival al Qaeda and its leadership while imploring Islamic State supporters to take up arms and launch attacks in their home countries, from Australia to France.

Tuesday’s statements, posted to both the terror group’s official Amaq News Agency and its Aleppo Province media arm, didn’t say when Adnani had died. They didn’t detail how he was killed or which side in Syria’s multifaceted conflict was responsible for his death.

“The blood of the sheiks will only make it more firm on the path of jihad and determination to take revenge and assault,” it said.

Syrian rebel factions and President Bashar al-Assad’s regime have fought a yearslong war of attrition for the northern city of Aleppo. U.S. coalition, Russian and Syrian airstrikes pound Aleppo province regularly, with Lebanon’s Hezbollah, Kurdish and Arab rebels fighting on the ground.

Islamic State’s statement Tuesday referred to Adnani for the first time as a descendant of the Prophet Muhammad. That bloodline would give him important standing among jihadists, as key Islamic texts addressing the apocalypse claim a descendant of the prophet will rule as caliph, or religious emperor.

The religious title is claimed by Abu Bakr al-Baghdadi, who in 2014 declared a caliphate stretching across Syria and Iraq.

The lineage claim may mean Adnani was being positioned as the successor to Mr. Baghdadi, William McCants, a director at the Brookings Institution, said on Twitter.

The impact of Adnani’s death on Islamic State’s operations remains to be seen. Terror organizations from Hezbollah to Islamic State tend to be well-prepared to weather leadership changes, even in senior ranks. Al Qaeda continues to launch successful operations after the 2011 death of former leader Osama bin Laden.

Sen. Richard Burr (R., N.C.), chairman of the Senate Intelligence Committee, said Adnani’s removal could disrupt some of the group’s attack plotting.

“It’s at this early stage difficult to know quite what the implications of his death will be, beyond symbolism,” said Charlie Winter, a terror analyst who studies the group. “Islamic State’s leadership prides itself on its organizational opacity, so it is crucial that we don’t overstate the immediate tactical consequences of his death.”

Adnani was born as Taha Sobhi Falaha in Syria sometime in the late 1970s. He was put on the U.S. State Department’s terrorist designation list in August 2014.

“Adnani was one of the first foreign fighters to oppose [U.S.-led] coalition forces in Iraq before becoming ISIL’s spokesman,” the U.S. State Department said when blacklisting him, using an acronym for Islamic State.

His involvement with Islamic State dates back over a decade, when the U.S. invaded Iraq in 2003 and regional jihadists flocked to the country to take up arms against American soldiers with the group’s predecessor, al Qaeda in Iraq.

Adnani helped al Qaeda in Iraq rise to prominence as al Qaeda’s most brutal faction during the peak of the country’s civil war from 2004 to 2007. He emerged as Islamic State’s spokesman after the group’s very public divorce from al Qaeda in 2013.

Islamic State quickly became known for amplifying al Qaeda’s brutality, subjecting Muslims and religious minorities under its rule to beheadings, crucifixions and more for defying its rule.

In a widely distributed speech in 2014, Adnani urged followers to kill Westerners and non-believers any way possible. “Smash his head with a rock, or slaughter him with a knife, or run him over with your car, or throw him down from a high place, or choke him, or poison him,” he said, according to SITE, a group that monitors militant web sites.

Wall Street Journal