In this article we estimate the influence of leadership changes on the operational dynamics
associated with terrorist attacks conducted by the Islamic State and its predecessors. Because
the focus of our research is empirical, the study uses data for 2,131 successful attacks
between October 2002 and December 2014 to examine differentials in operational tempo,
attack severity, primary tactics employed, and principal targets. The data are aggregated on a
monthly basis to estimate the probabilities associated with specific attack sequences in terms
of the following primary tactics: (1) firearms, (2) explosives, (3) hostage-taking/kidnapping,
and (4) attacks involving combinations of (1), (2), and/or (3). The analysis is placed in a
broad historical and strategic context in order to explore two key issues: (1) The effect of
leadership change on terrorist group activity and (2) The implications for counterterrorism
and counterinsurgency efforts. Our analysis reveals a myriad of conceptual, theoretical, and
policy implications.