The meeting, said to have occurred in mid-2017, was the third convening of a committee that had been a pet project of the man at the top, having been "established by caliph Abu Bakr al-Baghdadi," the officer said.
The incident provides a rare glimpse into the secluded life of the Isis leader, a man who has allowed himself to be photographed only once, in July 2014, and has spoken publicly only a handful of times since then.
His prolonged absences have given wings to countless false reports portraying Baghdadi as either dead, or gravely wounded and incapacitated.
Despite such rumours, US counterterrorism officials are convinced that Baghdadi is alive and is helping direct long-term strategy for the dwindling numbers of Isis fighters defending the group's remaining strongholds in eastern Syria.
The US view is supported by intelligence intercepts and detainee interrogations, as well as writings and statements by operatives within the terrorist group's network.
The evidence, while spotty and difficult to confirm, depicts a leader who has opted to make himself invisible, even within his organisation - a decision that has drawn complaints from followers and arguably undercuts his ability to rally his beleaguered forces, terrorism experts say.
But the intercepts and reports also suggest that Baghdadi has shifted his attention in recent months to crafting an ideological framework that will survive the physical destruction of the caliphate in Iraq and Syria.
In addition to his effort to revamp the group's school curriculum, Baghdadi appears to have been behind a series of missives in recent months that sought to settle ideological disputes between factions of Isis fighters.
Viewed together, such actions convey the impression of a disciplined retreat, with Baghdadi helping manage preparations for a shift from caliphate to underground insurgency and international terrorist movement, current and former US officials said.
"Even as they were losing Mosul and Raqqa, we were seeing indications that they were planning to operate anew, as a clandestine organisation," said Nicholas Rasmussen, who served as director of the National Counterterrorism Centre before stepping down in December.
"As they were being driven out of these places, they were leaving behind a kind of cell structure."
The essential strategy also was confirmed by a self-proclaimed Isis operative contacted by the Washington Post through an encrypted messaging service.
The operative said Baghdadi - a university professor before becoming a terrorist - and other top leaders decided early on to prioritise the indoctrination of children and recruits, both inside Iraq and Syria and also abroad, through the Internet.
The effort gained additional urgency as it became clear that the group's Islamist enclave would not survive, he said.
"The leadership is convinced that, even if the State has disappeared, as long as they can influence the next generation through education, the idea of the caliphate will endure," said the operative.
Under Baghdadi's direction, "the values of the caliphate would be seeded in the Umma [Islamic community], and not disappear," the operative said, "even if the caliphate would."
"By all indications, [Baghdadi's] alive," said a US counterterrorism official. "We think he's still coordinating, still helping to run the organisation."
In late 2016, the raising of the bounty for Baghdadi's capture - from US$10 million to US$25 million - triggered a flurry of reported sightings, none of which panned out. Since then, there have been few credible reports about his specific movements and activities, the official acknowledged.
"Our best guess is that he is still in Syria, in one of the remaining parts of the country still controlled by Isis," the official said.
Some observers see Baghdadi's absence as part of a deliberate strategy within an organization that in recent years has chosen to de-emphasise the importance of individual leaders in advancing the group's ideals.
"A lot of Isis supporters say that Baghdadi doesn't want to make Isis all about him," said Cole Bunzel, a Middle East scholar at Princeton University and editor of Jihadica, a scholarly blog about the global jihadist movement. "There has been an effort, in fact, not to elevate any one personality above the organisation."
Yet Baghdadi's virtual invisibility during a crucial struggle for the group's survival has stirred controversy within Isis itself. In recent weeks, members of an Isis offshoot in Deir al-Zour have posted messages on social media complaining that Baghdadi has removed himself from the field of battle.
"This clearly affects the morale of Isis and its supporters," said Steven Stalinsky, executive director of the Middle East Media Research Institute, a Washington nonprofit that monitors jihadists' websites.
Other supporters have responded to the criticism by renewing their oaths of allegiance to Baghdadi, in what Stalinsky described as a possible "indication that he is, or was, facing challenges to his authority from within."
Rasmussen said the slow-but-steady military campaign against Isis has given Baghdadi ample opportunities to develop secure lines of communication and to prepare for the future.
Those preparations probably include plotting future terrorist operations and honing a system for persevering and disseminating the group's core ideas after Isis ceases to exist as a caliphate.
"They knew this was happening - it wasn't as though they had a theory of victory where they were going to hold Mosul and Raqqa forever," Rasmussen said.
"But the narrative that has underpinned the Sunni extremist project - whether it's al-Qaeda or Isis - is that the mantle is going to be picked up and advanced by some other set of actors. The project may not be tied to the Syria conflict, but it's not going to go away just because Isis is defeated on the battlefield."
