Ed Crenshaw
Craig Jenkins

Principal Investigators: Edward Crenshaw, J. Craig Jenkins

Although international terrorism has been a phenomenon for decades, the origin of the terrorists, their motivation, and their targets have changed. During the Cold War, most terrorists acts were Marxist or Leftist; however, since the early 1990s, the majority have been ethno-Islamic. For this reason, scholars have begun to discuss “waves of terror.”

In “Terror’s Fourth Wave,” Crenshaw and Jenkins focused on ethno-Islamic terrorism by sampling only countries with a sizeable Muslim population -– either 70 nations with populations at least 10 percent Muslim, or 40 nations at least 50 percent Muslim.

They started the project by using the International Attributes of Terrorism Database to identify all acts of international terrorism carried out by citizens of these countries from 1968-2003. They then used the ITERATE database to identify the location of the attack, its nature, target, number of casualties, and ideologies of the groups involved.

Once the data set was assembled, Crenshaw and Jenkins conducted two investigations:
• Identifying the share of global acts of terrorism for the entire region as well as each country, broken down by target (American, Western, non-Western).
• Identifying the share of global casualties due to terrorism for the entire region as well as each country, broken down by target (American, Western, non-Western).

The ultimate goal was to determine the motivations for ethno-Islamic terrorism, and whether these motivations differ by target. Crenshaw and Jenkins found four triggering factors: a large secular government, greater rights for women, dependence on Western military support, and a sizeable but not dominant Muslim population.

An early version of their results was published in Kristopher K. Robison, Edward M. Crenshaw, and J. Craig Jenkins, “Ideologies of Violence: The Social Origins of Islamist and Leftist Transnational Terrorism,” Social Forces, June 2006. Crenshaw and Jenkins also have a pending grant from the National Science Foundation for a broader study.