That the Islamic State can easily survive the loss of its top leader is not as straightforward a proposition as seems to be widely believed. Mr. al-Baghdadi’s death, almost exactly seven months after the obliteration of the physical caliphate he built, comes at an exceptionally bad time. The organization is still struggling to recover from the collapse of its caliphate and the deaths of many top leaders. It is fragile, caught somewhere between being a proto-state and a full-fledged insurgency.

Mr. al-Baghdadi’s oversight was vital in guiding ISIS’s current transition from governing body to effective underground organization. Captured commanders have testified to Iraqi and Kurdish troops about his involvement in day-to-day affairs, and the meetings he held with different regional heads. Under his watch, the group was able to maintain its control over a sprawling range of affiliates, from Afghanistan to Nigeria, despite the tumultuous collapse of the caliphate in Iraq and Syria. He also prevented internal ideological differences from spiraling out of control. Holding the organization together may not be so easy with him out of the picture.

But it is true that the Islamic State has been prepared for some time to go on without its leader.