He's examined every single incident of suicide terrorism from the early 80's to today. He finds that foreign military occupation is the primary cause of suicide terrorism. For instance, many people don't know this, but the most prolific suicide terrorist organization prior to 9/11 was the Tamil Tigers of Sri Lanka. This is group is expressly secular. However they live in a region that they regard as being occupied by an outside military, that of the Sri Lankan government. He shows that the presence of American military forces for combat operations on the homeland territory of the suicide terrorists is stronger than Islamic fundamentalism in predicting whether individuals from that country will become al-Qaeda suicide terrorists by a factor of 10 to 1.