Sullivan, the national security adviser, was there with other White House staff, while Cabinet members participated via secure hookups.

The principals meeting kicked off with an intelligence briefing concluding that the situation was so “fluid” that the Afghan government’s seat of power in Kabul could fall “within weeks or days,” the official noted.

That was a far cry from the assessments officials were relying on just days earlier that estimated a Taliban takeover would take months, or even up to two years, following the withdrawal of American and NATO troops. As recently as Aug. 8, McKenzie sent Austin a new, more pessimistic estimate: that Kabul could be isolated within 30 days.

“It was a pretty sobering meeting,” the official said. “We thought we had months ahead of us to draw down the embassy and do processing and relocation.”