Employing counterfactuals to assess individual and systemic explanations for the split between Al Qaeda and the Islamic State of Iraq and al-Sham (ISIS), this article concludes that individual leaders factor greatly into terrorist alliance outcomes. Osama bin Laden was instrumental in keeping Al Qaeda and ISIS allied as he prioritized unity and handled internal disputes more deftly than his successor, Dr. Ayman al-Zawahiri. Although a troubled alliance, strategic differences between Al Qaeda and ISIS were not sufficient to cause the split. Rather, the capabilities of Al Qaeda's leader determined the group's ability to prevent alliance ruptures.
Bacon, Tricia and Elizabeth Grimm Arsenault. 2017. "Al Qaeda and the Islamic State's Break: Strategic Strife or Lackluster Leadership?" Studies in Conflict & Terrorism (October). https://www.tandfonline.com/doi/abs/10.1080/1057610X.2017.1373895