President Joe Biden’s surprise announcement Monday night—that a U.S. drone strike over the weekend killed Ayman al-Zawahiri, leader of al-Qaida and co-architect of the 9/11 terrorist attack—is both more and less significant than it might seem at first glance.

On the one hand, mainly because of the West’s counter-terrorism strategies, al-Qaida is far from the potent global force that it was a decade ago. Its presence has been muted, and Zawahiri himself has hidden so far out of sight that one prominent expert speculated back in November that he might have been killed already.

On the other hand, one fact about this drone strike hints at a much larger finding: It took place in Afghanistan. It turns out Zawahiri was living with his family in a large safehouse in downtown Kabul—meaning he had to be there with the Taliban’s full blessing. This means that, contrary to the Taliban’s assurances, they have been plotting a revival of their alliance with al-Qaida—the alliance that Osama bin Laden formed at the turn of the century and that spawned the attack on the World Trade Center.