The question began to swirl immediately after Egyptian-born terrorist Ayman al-Zawahiri was killed in a US drone strike on Kabul in July 2022: Who will succeed the al-Qaeda leader who himself succeeded founder Osama bin Laden in 2011?
 
In their groundbreaking new book, Terror in Transition: Leadership and Succession in Terrorist Organizations, School of Public Affairs professor Tricia Bacon and Georgetown University professor Elizabeth Grimm pose an even more consequential question—one long overlooked by scholars and media pundits alike.
 
What kind of leader will emerge after the founder of a religious terrorist group is killed, exiled, or removed from power?
 
The book, released in September, offers a new theoretical framework for analyzing the role of founders in establishing the group’s objective (the why) and determining the tactics and resources necessary to achieve it (the how). Bacon and Grimm also examine how terrorist groups adapt to major shifts in leadership under varying levels of counterterrorism pressure and whether successors choose to pursue incremental change, a natural progression of what the founder intended, or discontinuous change, a more radical shift, to the organization’s mission and methods. 
 
“We are not simply interested in who the successor is, but in the way they lead,” says Bacon, who teaches in SPA’s Department of Justice, Law, and Criminology. “Will they continue to lead the organization in the same way that the founder intended, or will they take steps to change the organization’s how and why?”
 
Bacon and Grimm analyzed the interaction of those factors—incremental or discontinuous changes to the how and the why—and from that matrix developed five types of successors. 

• A caretaker continues the leader’s trajectory and makes only incremental changes to the how and the why. These are individuals for whom authority, prestige, and legitimacy have typically been passed down from the founder. 
• A signaler makes discontinuous change to the why—adopting new rhetoric, for example, or pledging affiliation to a different organization—but only incremental changes to the how. 
• A fixer makes incremental changes to the why but discontinuous changes to the how, perhaps introducing IEDs or female suicide bombers or moving to a new area to raise money and recruit.
• A visionary makes discontinuous changes to both the why and the how. This could include proclaiming the formation of a state and introducing governance to the repertoire of action. 
•  A figurehead is absent and refrains from any decision making. This type of leader could emerge because the founder is imprisoned or ill. 

The researchers applied this framework to a sample of more than 90 leaders of 33 religious terrorist organizations—including the second Ku Klux Klan, the Egyptian Islamic Jihad, and Al-Shabaab—that span more than 20 nation-states and 100 years. They were surprised to find that caretakers and fixers emerge most often as successors, indicating that “these groups are more conservative than you might think, given their revolutionary aims,” says Bacon, director of AU’s Policy Anti-Terrorism Hub. 
 
The framework has important implications for counterterrorism—a field in which Bacon worked for more than a decade with the Department of State before joining AU. “Since 9/11, the policy on leadership decapitation has been to do it when you can,” she says. “But that’s not going to be the strategy anymore because there just aren’t the resources.” By analyzing the kind of successor who emerges during a leadership transition—the time at which groups are most vulnerable—and their fit for the organization’s circumstances, counterterrorism officials can determine whether it’s worth eliminating them. 
 
“When you have somebody who’s a visionary and departed so far from the founder’s how and why, that creates opportunities to exploit for counterterrorism practitioners in terms of their divisiveness. When you have a figurehead who’s not doing very much, that can be a way to discredit that individual,” Bacon says. “Each type of successor creates some counterterrorism opportunity.”