"It may be religious, as was certainly the case with the September 11 plotters; it may involve obsessive loyalty to a political leader, as was true of those who killed themselves for the almost cult-like PKK and its head, Abdullah Ocalan. ......The Turkish success in defeating the PKK's suicide campaign is also frequently cited by experts. The Turks combined a program of concessions to Kurdish aspirations in the region with an intense, focused counterinsurgency campaign aimed at isolating and ultimately capturing the PKK leader Abdullah Ocalan. And once they had him, they didn't kill him but put him on trial. Pedahzur wholeheartedly approves, pointing out that extrajudicial killing of terrorist leaders—as with Hamas officials in Israel—merely creates new generations of martyrs and undermines the moral claims of the democracies....."
More:The New York Review of Books: Why They Do It