Trajectories of Terrorism: Attack Patterns of Foreign Groups That Have Targeted the United States, 1970-2004

Although researchers began to assemble open-source terrorism event databases in the late 1960s, until recently most of these databases excluded domestic attacks. This exclusion is particularly misleading for the United States because, although the United States is often perceived to be the central target of transnational terrorism, the domestic attacks of foreign groups targeting the United States are often ignored. We began this article with 53 foreign terrorist groups that have been identified by U.S. State Department and other government sources as posing a special threat to the United States. Using newly available data from the Global Terrorism Database composed of both domestic and transnational terrorist attacks, we examined 16,916 attacks attributed to these groups between 1970 and 2004. We found that just 3% of attacks by these designated anti-U.S. groups were actually directed at the United States. Moreover, 99% of attacks targeting the United States did not occur on U.S. soil but were aimed at U.S. targets in other countries (e.g., embassies or multilateral corporations). We also found that more than 90% of the non-U.S. attacks were domestic (i.e., nationals from one country attacking targets of the same nationality in the same country). We used group-based trajectory analysis to examine the different developmental trajectories of U.S. target and non-U.S. target terrorist strikes and concluded that four trajectories best capture attack patterns for both. These trajectories outline three terrorist waves—which occurred in the 1970s, 1980s, and the early 21st century—as well as a trajectory that does not exhibit wave-like characteristics but instead is characterized by irregular and infrequent attacks.