The War Comes Home: The Evolution of Domestic Terrorism in the United States

CSIS Briefs

The Issue

White supremacists and other like-minded extremists conducted two-thirds of the terrorist plots and attacks in the United States in 2020, according to new CSIS data. Anarchists, anti-fascists, and other like-minded extremists orchestrated 20 percent of the plots and attacks, though the number of incidents grew from previous years as these extremists targeted law enforcement, military, and government facilities and personnel. Despite these findings, however, the number of fatalities from domestic terrorism is relatively low compared to previous years.


There has been growing concern about the threat of domestic terrorism, with extremists motivated by political, racial, ethnic, economic, health, and other grievances. In October 2020, the FBI arrested Adam Fox, Barry Croft, and several other accomplices in a plot to kidnap and potentially execute Michigan Governor Gretchen Whitmer. Members of this network, which had ties to militias in Michigan and other states, referred to Governor Whitmer as a “tyrant” and claimed that she had “uncontrolled power right now.”1 They also discussed kidnapping Virginia Governor Ralph Northam, in part because of his lockdown orders to slow the spread of Covid-19.2

Some U.S. government agencies have outlined the threat from domestic extremists, though most have not provided recent data about terrorist incidents. In its Homeland Threat Assessment released in October 2020, the U.S. Department of Homeland Security concluded that “racially and ethnically motivated violent extremists—specifically white supremacist extremists (WSEs)—will remain the most persistent and lethal threat in the Homeland.”3 The report also assessed that anarchists and other individuals inspired by anti-government and anti-authority ideologies posed a threat. But it did not provide 2020 data. The Federal Bureau of Investigation similarly argued that the “top threat we face from domestic violent extremists” is from racially- and ethnically-motivated violent extremists, including white supremacists.4 Nevertheless, FBI officials have not publicly released their data, making it difficult for U.S. civilians to judge the degree and type of threat.

To help fill this gap, this analysis provides new data on the domestic terrorist threat in the United States. It asks several questions. What are the main trends in domestic terrorism in 2020 in such areas as terrorist motivation, tactics, and targets? How did 2020 compare to previous years? To answer these questions, the authors constructed a data set of terrorist attacks and plots in the United States from January 1, 2020 to August 31, 2020, which updated a broader CSIS data set of terrorist incidents in the United States from 1994 to 2020.5

Based on the data, this analysis has several findings, which are discussed at greater length later in this assessment. First, white supremacists and other like-minded extremists conducted 67 percent of terrorist plots and attacks in the United States in 2020. They used vehicles, explosives, and firearms as their predominant weapons and targeted demonstrators and other individuals because of their racial, ethnic, religious, or political makeup—such as African Americans, immigrants, Muslims, and Jews. Second, there was a rise in the number of anarchist, anti-fascist, and other like-minded attacks and plots in 2020 compared to previous years, which comprised 20 percent of terrorist incidents (an increase from 8 percent in 2019). These types of extremists used explosives and incendiaries in the majority of attacks, followed by firearms. They also targeted police, military, and government personnel and facilities. Third, far-left and far-right violence was deeply intertwined—creating a classic “security dilemma.”6 Since it is difficult to distinguish between offensive and defensive weapons, armed individuals from various sides reacted to each other during protests and riots, and each side’s efforts to protect itself and acquire weapons generally threatened others.

Despite these findings, this violence needs to be understood in historical context. The number of fatalities from terrorist attacks in the U.S. homeland is still relatively small compared to some periods in U.S. history, making it important not to overstate the threat.7 Roughly half of the years since 1994 had a greater number of fatalities from terrorism than 2020—at least between January 1 and August 31, 2020. There were also no mass-casualty terrorist attacks, a stark contrast from such incidents as the April 1995 Oklahoma City bombing, which killed 168 people; the September 2001 attacks, which killed nearly 3,000 people; and the June 2016 Orlando attack, which killed 49 people. Still, violence levels in the United States could rise over the next year depending on political polarization, the persistence of the Covid-19 pandemic (and reactions to policy decisions to mitigate its spread), worsening economic conditions, growing concerns about immigration (whether real or perceived), racial injustice, or other factors. It is also possible that the organizational structure of extremism could evolve from today’s decentralized landscape to include more hierarchically structured groups.

The rest of this report is divided into three sections. The first defines terrorism and differentiates this report’s focus on terrorism from other phenomena, such as hate crimes and riots. The second section outlines and analyzes the 2020 terrorism data. The third explores future developments, including the potential for violence after the 2020 presidential election.

Defining Terrorism

This report focuses on terrorism—not other issues, such as hate crimes, protests, riots, or broader civil unrest. Terrorism is the deliberate use—or threat—of violence by non-state actors in order to achieve political goals and create a broad psychological impact.8 Violence and the threat of violence are important components of terrorism. This analysis divides terrorism into several categories: religious, ethnonationalist, violent-far-right, violent-far-left, and other (which includes terrorism that does not fit neatly into any of the other categories).9 Terms such as far-right and far-left terrorism do not correspond to mainstream political parties in the United States, such as the Republican and Democratic parties, which eschew terrorism. Nor do they correspond to the vast majority of political conservatives and liberals in the United States, who do not support terrorism. Instead, terrorism is orchestrated by a small set of violent extremists. As terrorism scholar Walter Laqueur argues, “terrorist movements are usually small; some very small indeed, and while historians and sociologists can sometimes account for mass movements, the movements of small particles in politics as in physics often defy any explanation.”10

Religious terrorism includes violence in support of a faith-based belief system, such as Islam, Judaism, Christianity, or Hinduism. The primary threat from religious terrorists in the United States comes from Salafi-jihadists inspired by the Islamic State and al-Qaeda.11 Ethnonationalist terrorism refers to violence in support of ethnic or nationalist goals, which often include struggles of self-determination and separatism along ethnic or nationalist lines. Due to the relatively low levels of ethnonationalist terrorism in the United States—no such incidents occurred in 2020—this brief does not address ethnonationalist terrorism.12 Far-right terrorism refers to the use or threat of violence by subnational or non-state entities whose goals may include racial or ethnic supremacy; opposition to government authority; anger at women, including from the involuntary celibate (or “incel”) movement; belief in certain conspiracy theories, such as QAnon; and outrage against certain policies, such as abortion.13 Some extremists on the violent far-right have supported “accelerationism,” which includes taking actions to promote social upheaval and incite a civil war.14 Far-left terrorism involves the use or threat of violence by subnational or non-state entities that oppose capitalism, imperialism, and colonialism; advocate black nationalism; pursue environmental or animal rights issues; espouse pro-communist or pro-socialist beliefs; or support a decentralized social and political system such as anarchism.15 Other involves the use or threat of violence by subnational or non-state entities that do not neatly fit into any of the above categories, such as the anti-government Boogaloo movement, whose adherents aim to start a civil war (or “boogaloo”) in the United States.16

In focusing on terrorism, this report does not cover the broader categories of hate speech or hate crimes. There is some overlap between terrorism and hate crimes, since some hate crimes include the use or threat of violence.17 But hate crimes can also include non-violent incidents, such as graffiti and verbal abuse. Hate crimes and hate speech are obviously concerning and a threat to society, but this analysis concentrates only on terrorism and the use—or threat—of violence to achieve political objectives. In addition, this analysis does not focus on protests, looting, and broader civil disturbances. While these incidents are important to analyze—particularly in light of the events in 2020 following the death of George Floyd—most are not terrorism. Some are not violent, while others lack a political motivation. For instance, some of the looting following the death of George Floyd was perpetrated by apolitical criminals.18 Nevertheless, coding incidents as terrorism is challenging in some cases, which is addressed in the methodology that accompanies this analysis.

Finally, while there is often a desire among government officials and academics to focus on terrorist groups and organizations, the terrorism landscape in the United States remains highly decentralized. Many are inspired by the concept of “leaderless resistance,” which rejects a centralized, hierarchical organization in favor of decentralized networks or individual activity.19 As Kathleen Belew argues in her study of the white power movement in the United States, the aim of leaderless resistance is “to prevent the infiltration of groups, and the prosecution of organizations and individuals, by formally dissociating activists from each other and by eliminating official orders.”20 In addition to their decentralized structures, the violent far-right and far-left in the United States include a wide range of ideologies. The decentralized nature of terrorism is particularly noteworthy regarding the use of violence, which CSIS data suggests is often planned and orchestrated by a single individual or small network. Consequently, this analysis frequently refers to terrorist individuals and networks, rather than groups.

Data Analysis

To evaluate the terrorism threat in the United States, CSIS compiled a data set of 61 incidents that occurred in the country between January 1 and August 31, 2020. (The link to the methodology can be found at the end of the brief.) These incidents included both attacks and plots. The authors coded the ideology of the perpetrators into one of four categories: religious, violent far-right, violent far-left, and other (there were no ethnonationalist attacks or plots during this period). All religious attacks and plots in the CSIS data set were committed by terrorists motivated by a Salafi-jihadist ideology. Of the four attacks coded as “other,” all were committed by adherents of the Boogaloo movement. This section analyzes the data in three parts: number of attacks and plots, targets and tactics, and fatalities.

Attacks and Plots: Most domestic terrorist attacks and plots between January 1 and August 31, 2020 were committed by white supremacists, anti-government extremists from the violent far-right, and involuntary celibates (incels). As shown in Figure 1, far-right terrorists committed 67 percent of attacks and plots, far-left terrorists committed 20 percent, and extremists with other motivations (such as supporters of the Boogaloo movement) and Salafi-jihadists each committed 7 percent.

In mid-January 2020, six members of The Base, a transnational white supremacist group, were arrested in Georgia and Maryland and charged with plotting terrorist attacks.21 On May 8, the FBI arrested anti-government extremist Christian Stanley Ferguson in Cleveland, Ohio, who was planning to ambush and execute federal law enforcement officers and then start an uprising.22 Ferguson also posted violent messages on the digital distribution platform Discord. In one of three attacks in 2020 linked to the online “manosphere,” Armando Hernandez, Jr. was arrested in Glendale, Arizona, after a shooting spree targeting couples at the Westgate Entertainment District that injured three individuals.23

Targets and Tactics: The increase in protests and political rallies over the summer of 2020 resulted in notable changes in targets and weapons adopted by violent far-left and far-right extremists.

Actors of both orientations targeted demonstrators in a large percentage of their attacks.24 Demonstrators were the primary targets of far-right terrorists—in 50 percent of attacks and plots—including attacks from white supremacists and others who opposed the Black Lives Matter movement. For example, on May 30 Brandon McCormick threatened Black Lives Matter protesters in Salt Lake City, Utah, with a knife and a loaded compound bow while shouting racial slurs.25 As in previous years, violent far-right extremists frequently targeted government, military, and police targets (18 percent of incidents) and private individuals based on race, gender, and other factors (18 percent of incidents).

While the primary targets (58 percent) of anarchists and anti-fascists were police, government, and military personnel and institutions, 42 percent of their attacks and plots in 2020 also targeted demonstrators. These included crowds supporting the police and Donald Trump, as well as protesters against abortion. The rise in violent far-left and far-right attacks against demonstrators may have been caused by the emerging security dilemma in urban areas, where there was a combustible mix of large crowds, angry demonstrators, and weapons.

There was also an increase in vehicle attacks, most of which targeted demonstrators and most of which were committed by white supremacists or others who opposed the Black Lives Matter movement. On June 7, for instance, Harry H. Rogers—a member of the Ku Klux Klan—intentionally drove his blue Chevrolet pick-up truck into a crowd of Black Lives Matter protesters, injuring one.26 Rogers was later convicted and sentenced to six years in prison. From January to August 2020, vehicles were used in 11 violent far-right attacks—27 percent of all far-right terrorist incidents—narrowly making them the weapons most frequently used in far-right attacks. This marked a significant increase from 2015 to 2019, during which a vehicle was used in only one violent far-right attack. Although vehicle attacks against demonstrators were most common among white supremacists, one such attack was committed by a violent far-left perpetrator as well. On July 25, Isaiah Ray Cordova drove his sports utility vehicle into a crowd in Eaton, Colorado, which had gathered for a Defend the Police rally.27

This spike in vehicle attacks may have been caused by the ease of using a vehicle to target large gatherings, such as protests. As a Department of Homeland Security assessment concluded, “Attacks of this nature require minimal capability, but can have a devastating impact in crowded places with low levels of visible security.”28 While a concerning development, these vehicle attacks were not as lethal as those in such cities as Nice, France in July 2016, which killed 86 people; Barcelona in August 2017, which killed 16 people; or New York City in October 2017, which killed 8 people.

Explosives, incendiaries, and firearms remained common in both violent far-right and violent far-left attacks and plots, despite the increase in vehicle attacks linked to rallies and protests. Firearms were used in nearly a quarter of violent far-right incidents and were used in 34 percent of violent far-left attacks and plots. On June 6, local police arrested Brandon Moore in Coos Bay, Oregon, after he threatened protesters with a handgun while saying, “White lives matter.”29 Meanwhile, explosives and incendiaries were used in half of far-left incidents—all of which targeted government or police property or personnel—and in 25 percent of violent far-right attacks and plots. On May 28, far-left extremists in Minneapolis, Minnesota, conducted an arson attack against the Minneapolis Police Department’s Third Precinct, as the crowd shouted “Burn it down, burn it down.”30 The U.S. Department of Justice charged four men—Dylan Shakespeare Robinson, Davon De-Andre Turner, Bryce Michael Williams, and Branden Michael Wolfe—with conspiracy to commit arson and other crimes in the attack at the Third Precinct.31

Overall, the data suggest that domestic terrorism evolved based on the surge in public demonstrations that began in May. These trends were not a commentary on the protests themselves, but rather on the ability of extremists to adapt to opportunities and the proximity of armed individuals in cities with different political and ideological motivations. Data compiled by the Armed Conflict Location and Event Data Project (ACLED) found that out of 10,600 demonstrations between May and August, nearly 95 percent were peaceful, while approximately 5 percent—fewer than 570—involved violence.”32

Fatalities: Despite the large number of terrorist incidents, there were only five fatalities caused by domestic terrorism in the first eight months of 2020. There were four times as many far-left terrorist incidents and the same number of far-right terrorist incidents in 2020 as in all of 2019. Yet only 5 of the 61 incidents (8 percent) recorded between January and August 2020 resulted in fatalities, excluding the perpetrator. Some of these incidents were plots foiled by the FBI or other law enforcement agencies, which suggested that law enforcement agencies were effective in preventing several major attacks. Still, the number of fatalities in 2020 was low compared to the past five years, in which total fatalities ranged from 22 to 66 fatalities. All five fatal attacks in 2020 were conducted with firearms.33

Of the five fatal attacks—each of which resulted in the death of one individual—one was committed by an Antifa activist, one by a far-right extremist, one by an anti-feminist, and two by an adherent of the Boogaloo movement.34 In the fatal far-left attack, Michael Reinoehl, an Antifa extremist, shot and killed Aaron “Jay” Danielson in Portland, Oregon, on August 29.35 On July 25, Daniel Perry shot and killed a protester in Austin, Texas.36 On July 19, anti-feminist Roy Den Hollander shot the family of U.S. District Judge Esther Salas, killing her son and wounding her husband.37 Finally, there were two fatal Boogaloo attacks in 2020. On May 29, Steven Carrillo shot and killed Pat Underwood, a protective security officer, and wounded his partner in Oakland, California.38 Carrillo also killed a Santa Cruz County Sherriff’s Deputy in Ben Lomond, California, with an assault rifle on June 6, 2020.39

The relatively low number of fatalities compared to the high number of terrorist incidents suggests that extremists in 2020 prioritized sending messages through intimidation and threats rather than killing. Given that a large portion of attacks were conducted with vehicles or firearms, there was a high potential for lethality—but an apparent lack of will.

Future Developments

A growing number of U.S. federal and state threat assessments have concluded that domestic terrorism could persist in the United States for the foreseeable future, including in 2021 and beyond. For example, the New Jersey Office of Homeland Security and Preparedness projected that “domestic extremists—primarily anarchist, anti-government, and racially motivated—will continue to manipulate national incidents” and remain a threat at least through 2021.40 Looking toward the future, there are several issues worth monitoring.

First, there are various scenarios for a continuation—and even a rise—of violence after the November 2020 elections, which could persist into 2021 and beyond. Rising political polarization, growing economic challenges, the persistence of Covid-19, and growing concerns about immigration could lead to a rise in domestic terrorism.

The actions of far-left and far-right extremists are likely to be interlinked as various sides respond to others during protests, riots, demonstrations, and online activity. There appears to be an assumption by some extremists that others are prepared to use force, which heightens the possibility of violence. All sides have access to firearms, incendiaries, crude explosives, and other weapons, and are willing to bring them to demonstrations. This situation is a classic security dilemma.41 Each side’s efforts to increase its own security and acquire weapons inadvertently threaten the other side. Since it may be difficult for individuals to distinguish between offensive and defensive arms, even efforts by one side to protect itself may motivate others to arm, creating a spiral of actions that leads to violence.42 As Figure 6 highlights, domestic terrorism incidents have not been isolated to specific geographic locations, suggesting that a rise in terrorism would likely be a national problem, not a regional one. The broad scope of domestic terrorism also makes it difficult to predict where future incidents will occur.

In the event of a Democratic presidential victory, the threat could involve specific attacks by radicalized white supremacists, militias, and other related individuals. In these incidents, the primary weapons—particularly for fatal attacks—are likely to be firearms and explosives, as highlighted in the 2020 militia plots against the governors of Michigan and Virginia. Based on data from the National Instant Criminal Background Check System (NICS), the number of firearm background checks for gun purchases spiked to its highest level ever in 2020—which doubled over the past decade.43 The pervasiveness of guns—including automatic weapons—is particularly concerning in the United States’ ultra-polarized political climate. Based on our data, the targets are likely to be demonstrators, politicians, or individuals based on their race, ethnicity, or religion—such as African Americans, Latinos, Muslims, and Jews.

In the event of a Republican presidential victory, for example, the primary threat may come from large-scale demonstrations in cities, some of which become violent. Anarchists, anti-fascists, and other far-left extremists have utilized digital platforms and other publications to argue that Donald Trump is a neo-fascist and that violence is legitimate.44 As the Antifa-aligned journal It’s Going Down argued, “Suddenly, anarchists and antifa, who have been demonized and sidelined by the wider Left have been hearing from liberals and Leftists, ‘you’ve been right all along.’”45 A Baltimore-based Antifa activist explained the use of violence as graduated and escalating: “You fight them with fists so you don’t have to fight them with knives. You fight them with knives so you don’t have to fight them with guns. You fight them with guns so you don’t have to fight them with tanks.”46 Anarchists, anti-fascists, and other far-left individuals and networks have increasingly used firearms—in addition to explosives and incendiary devices—in conducting attacks. In this scenario, the primary targets could be government, military, and police facilities and personnel.

Digital platforms will likely continue to be a major battlefield. Far-left extremists will likely continue to use social media platforms—such as Reddit, Facebook, and Twitter—to release propaganda and instigate violence against political opponents, law enforcement, military, and the government.47 Many adopted slogans, such as ACAB (“all cops are bastards”), that were used in memes as part of their propaganda campaigns. Far-right extremists will likely use a multitude of mainstream platforms (such as Facebook, Twitter, Instagram, YouTube, Telegram, and Reddit), lesser-known platforms (such as Gab, Discord, Minds, and Bitchute), forums (such as Stormfront and IronForge), and other online communities to instigate violence against African Americans, Jews, immigrants, and others.48 Extremists from all sides will likely utilize digital platforms to fundraise, communicate, issue propaganda, conduct doxing campaigns (releasing an individual’s personally identifiable information), intimidate targets, and coordinate activity.

Second, the domestic landscape could shift from a decentralized milieu of extremists to more organized and hierarchically structured groups. As one study concluded, Louis Beam’s concept of “leaderless resistance” has been “a near total failure as a method of fomenting widespread armed resistance against the U.S. government.”49 Most effective militant organizations have established centralized organizational structures to enable their leaders to control how violence is orchestrated and how finances are secured and managed.50

In the United States, there are a handful of groups—such as The Base, the Atomwaffen Division (including rebranded versions such as the National Socialist Order), and the Feuerkrieg Division—with some leadership structure and command-and-control arrangements. There are also loose extremist movements that have a limited structure—especially in local areas or online—but lack a clear hierarchy and ideology. Examples include the Three Percenters, Oath Keepers, Boogaloos, QAnon, and some local networks of anarchists, anti-fascists, and militias. There have been some indications of greater organization, including the establishment of online hubs, such as MyMilitia, that provide a venue for individuals to find existing militias in the United States—or even to start their own.51

A shift toward more hierarchical groups could have at least two implications. It could increase the competence and professionalism of these organizations in numerous areas, such as planning attacks, recruiting, training, improving operational security, and fundraising. In the 1960s and 1970s, extremists in the United States established more centralized groups—such as the Order, Mau Mau, and White Knights—to improve their effectiveness.52 But research on terrorist and other militant groups indicates that centralized groups are more vulnerable to penetration by law enforcement and intelligence agencies.53

Fortunately, there is some good news. The number of fatalities from domestic terrorism today is relatively low, and the possibility of a civil war—which some experts have worried about and some extremists have predicted—is negligible.54 The United States has endured more violent periods in the past. Examples include a surge in white supremacist terrorism in the 1950s and 1960s (such as the Ku Klux Klan), black nationalist violence in the 1960s (such as the Black Liberation Army), revolutionary leftist violence in the 1960s and 1970s (such as the Weather Underground), and Puerto Rican nationalist violence in the late-1960s and 1970s (such as the Armed Forces of National Liberation, or FALN).55 In addition, the United States faced serious threats from Salafi-jihadists after September 11, 2001—such as Najibullah Zazi, Faisal Shahzad, Umar Farouk Abdulmutallab, Nidal Hasan, Omar Mateen, and Mohammed Alshamrani—who perpetrated or plotted mass-casualty attacks.

But the United States weathered these periods thanks to the resilience of Americans and the effectiveness of U.S. law enforcement, intelligence, and other national security agencies. During his second inaugural address, U.S. President Abraham Lincoln said it best in encouraging Americans to come together during divisive times:

With malice toward none; with charity for all; with firmness in the right, as God gives us to see the right, let us strive on to finish the work we are in; to bind up the nation’s wounds; to care for him who shall have borne the battle, and for his widow, and his orphan—to do all which may achieve and cherish, a just and lasting peace, among ourselves and with all nations.56

President Lincoln’s words are just as relevant today.

Seth G. Jones is the Harold Brown Chair and director of the Transnational Threats Project at the Center for Strategic and International Studies (CSIS) in Washington, D.C. Catrina Doxsee is a program manager and research associate with the Transnational Threats Project at CSIS. Nicholas Harrington is a program manager and research associate with the Transnational Threats Project at CSIS. Grace Hwang is a research assistant with the Burke Chair in Strategy at CSIS. James Suber is a research associate with the Transnational Threats Project at CSIS.

The authors give special thanks to Brian Michael Jenkins, Colin Clarke, Jacob Ware, and Alex Friedland for their review of the document—including the data set—and their helpful critiques. Also, thanks to David Brannan and Paul Smith for their comments.

For an overview of the methodology used in compiling the data set, please see here.

This brief is made possible by general support to CSIS. No direct sponsorship contributed to this brief.

CSIS Briefs are produced by the Center for Strategic and International Studies (CSIS), a private, tax-exempt institution focusing on international public policy issues. Its research is nonpartisan and nonproprietary. CSIS does not take specific policy positions. Accordingly, all views, positions, and conclusions expressed in this publication should be understood to be solely those of the author(s). 

© 2020 by the Center for Strategic and International Studies. All rights reserved.

Please consult the PDF for references.

Seth G. Jones
Senior Vice President; Harold Brown Chair; and Director, International Security Program
Catrina Doxsee
Fellow, Warfare, Irregular Threats, and Terrorism Program

James Suber

Research Assistant, Transnational Threats Project

Grace Hwang

Nicholas Harrington