Terrorists focus on five U.S. urban counties, but rural areas not exempt

attacks. “The 1970s were dominated by extreme left-wing terrorist attacks,” Bersani said. “Far left-wing terrorism in the U.S. is almost entirely limited to the 1970s with few events in the 1980s and virtually no events after that.”

Ethno-national/separatist terrorism was concentrated in the 1970s and 1980s, religiously motivated attacks occurred predominantly in the 1980s, extreme right-wing terrorism was concentrated in the 1990s, and single issue attacks were dispersed across the 1980s, 1990s, and 2000s, according to the new report.

To define the ideological motivations, LaFree and Bersani used START’s Profiles of Perpetrators of Terrorism — United States (Miller, Kathleen Smarick, and Simone, 2011), which briefly describes ideological motivations as:

Extreme right-wing: groups that believe that one’s personal or national “way of life” is under attack and is either already lost or that the threat is imminent (for some the threat is from a specific ethnic, racial, or religious group), and believe in the need to be prepared for an attack either by participating in paramilitary preparations and training or survivalism. Groups may also be fiercely nationalistic (as opposed to universal and international in orientation), anti-global, suspicious of centralized federal authority, reverent of individual liberty, and believe in conspiracy theories that involve grave threat to national sovereignty or personal liberty.

Extreme left-wing: groups that want to bring about change through violent revolution rather than through established political processes. This category also includes secular left-wing groups that rely heavily on terrorism to overthrow the capitalist system and either establish “a dictatorship of the proletariat” (Marxist-Leninists) or, much more rarely, a decentralized, non-hierarchical political system (anarchists).

Religious: groups that seek to smite the purported enemies of God and other evildoers, impose strict religious tenets or laws on society (fundamentalists), forcibly insert religion into the political sphere (for example, those who seek to politicize religion, such as Christian Reconstructionists and Islamists), or bring about Armageddon. For example, Jewish Direct Action, Mormon extremist, Jamaat-al-Fuqra, and Covenant, Sword and the Arm of the Lord (CSA) are included in this category.

Ethno-nationalist/separatist: regionally concentrated groups with a history of organized political autonomy with their own state, traditional ruler, or regional government, which are committed to gaining or regaining political independence through any means and who have supported political movements for autonomy at some time since 1945.

Single issue: groups or individuals that obsessively focus on very specific or narrowly-defined causes (for example, anti-abortion, anti-Catholic, anti-nuclear, anti-Castro). This category includes groups from all sides of the political spectrum.

— Read more in “Hot Spots of Terrorism and Other Crimes in the United States, 1970 to 2008” (College Park, Md.: University of Maryland, 31 January 2012)