A World of Terror is a graphical look at the 25 most impactful terrorist organizations since 1970, as defined by the National Consortium for the Study of Terrorism and Responses to Terrorism (START). START's Global Terrorism Database (GTD) includes incident-level data from open data sources around the world, spanning over 40 years.
Though the GTD has information for 3,065 groups, roughly half are perpetrators of only one incident. To determine the top 25 organizations who used terrorist tactics, the identified groups were with respect to the most recorded kills, wounded, and incidents; adding incidents made sure all actions were accounted for, including those that neither wounded nor killed.
These 3 lists were compiled and then the top organizations from each were used to generate the final set. Most of these organizations were in the top 30 for all 3 categories. While these 25 are less than 1% of all groups in the database, they account for over 26% of the 125,087 total incidents, and not surprisingly, contain several of the groups that are most active today.
Evolution of Groups: Many organizations evolve and change names, dissolve, or form splinter groups. Working with experts at START, the historical data was grouped into what they are commonly known as today. Two notable examples of this are:
ISIS: Tawhid and Jihad, Al-Qa'ida in Iraq, Islamic State of Iraq, and Islamic State of Iraq and the Levant are combined under the name ISIS. These are all the same group, but underwent name changes as it evolved over time. Although there were reportedly other smaller insurgent groups involved in the IS umbrella, these are commonly considered to be a (somewhat messy) evolution of the same organization.
FDN: The Nicaraguan Democratic Force (FDN) became part of the Nicaraguan Resistance umbrella group, and are thus grouped together. There were other contra groups involved in this alliance as well, but to simplify, these two very active groups have been used.