The recent death of Ayman al-Zawahiri marks a rare inflection point for a terrorist organization that has had just two leaders in the more than three decades of its existence. Forecasting its future trajectory—and developing counterterrorism policy—will depend on what type of leader emerges as Zawahiri's successor. Dr. Tricia Bacon and Dr. Elizabeth Grimm are the authors of a new book, Terror in Transition: Leadership and Succession in Terrorist Organizations. They join this episode to describe the five categories of leader they have identified by rigorously analyzing leadership succession in terrorist organizations. They also explain what each of those types of leader would mean for al-Qaeda going forward and why it is so crucial for counterterrorism policymakers and practitioners to understand these leadership types as they conceptualize the threat posed by the terrorist organization and seek ways to counter that threat.