It seems intuitive that a general strategy to combat insurgent groups would be to take out their leadership. Successful manhunts, like those that yielded Abu Musab al-Zarqawi and Osama bin Laden, have been greeted with much fanfare. But, as plenty of folks in the media are noticing in the past few days, it turns out some people have looked into the head-of-the-snake theory, and at least one of them--Jenna Jordan at the University of Chicago's--has findings that actually show the opposite.
Jordan looked at "leadership decapitation" (not to be confused with literal decapitation--this, instead, refers to the arrest or assassination of a group's leader) in over 298 cases between 1945 and 2004 in attempt to determine whether or not it lead to the collapse of the terrorist group at large. Here's an overview of some of her findings:
Decapitation does not increase the likelihood of organizational collapse beyond to a baseline rate of collapse for groups over time. The marginal utility for decapitation is actually negative. Groups that have not had their leaders targeted have a higher rate of decline than groups whose leaders have been removed. Decapitation is actually counterproductive, particularly for larger, older, religious, or separatist organizations.
She also found that decapitation was less successful against religiously-oriented groups than it was against ideological ones. Terrorist organizations with more than 500 members were more likely weather the loss of a leader as well.
The chart above is a quick visual we put together from her table comparing the rate of collapse for groups that experienced a leadership decapitation versus groups that did not, based on the age of the organization. (The Y-axis shows the percentage rate of collapse). Curiously, her data shows that collapse is actually less likely in the event of decapitation for groups less than 40 years old, as you can see in the two lines above. As Jordan puts it "groups are more likely to disintegrate absent decapitation." (For context: al Qaeda was founded around 1988 by bin Laden and estimates about the group's size range from several hundreds to several thousands, according to the Council on Foreign Relations.) Tom Jacobs at Miller-McCune compares Jordan's results to another opposing academic opinion here.