Of course, al-Qaida was never the only terrorist threat out there. More than 600 other groups have been engaged in terrorism worldwide since al-Qaida claimed its first attack in 1998. Other high-profile and extremely active groups have included the Shining Path in Peru, the IRA in Northern Ireland, and ETA in Spain. But in several respects, al-Qaida is unique. It has had the most global reach of any terrorist organization; it has specialized in high-profile, mass-casualty attacks; and it is probably the best-networked terrorist organization of all time.
Al-Qaida has also been especially ruthless in its disregard for human life. While al-Qaida has carried out fewer than 1 percent of all terrorist attacks since 1998, it has been responsible for more than 20 percent of terrorism fatalities.
Other modern terrorist organizations have taken many lives. For example, the Shining Path, the LTTE in Sri Lanka and the FMLN in El Salvador have all been responsible for thousands of deaths over the past 30 years. But al-Qaida has specialized in mass casualty attacks. Sixty-one groups have engaged in mass-casualty terrorism during this period, killing more than 25 people in a single strike. Al-Qaida has conducted more such strikes than any other group — 16 mass-casualty attacks in all. Looking at more than 85,000 terrorist attacks since 1970, the average number of people killed in an attack is two. In contrast, each al-Qaida attack has, on average, led to more than 50 deaths. Al-Qaida has taken the largest number of victims in the shortest amount of time of any terrorist organization in the modern era.
And finally, al-Qaida is likely the best-networked terrorist organization of all time. In many ways, al-Qaida operates like a franchise, with more than 30 direct links to and alliances with other terrorist organizations.
Even after bin Laden's death, al-Qaida's reach remains extensive, and the network that has formed around it is extremely dangerous. Collectively, these al-Qaida affiliates are now more deadly than the original organization, claiming more than 5,000 lives in recent years.
Even with the death of bin Laden, the many offshoots of al-Qaida are likely to continue their deadly attacks in the years ahead.
Article written and statistics compiled by Gary LaFree, Danielle Hawkins, Erin Miller and Kathleen Smarick of the National Consortium for the Study of Terrorism and Responses to Terrorism (START) at the University of Maryland, College Park.