Motivazioni ideologiche nel terrorismo americano 1970-2016

TERRORIST IDEOLOGIES BY DECADE
There were 2,794 terrorist attacks resulting in a total of 3,659 deaths in the United States between 1970 and 2016. More than four-fifths (82%) of the people killed in terrorist attacks in the United States during this time period died as a result of the September 11, 2001 attacks in New York, Pennsylvania, and Virginia. Additionally, 5 percent of deaths resulted from the 1995 bombing of the Alfred P. Murrah Federal Building in Oklahoma City, Oklahoma.
The graphs below show the ideological classification of terrorist attacks (top left) and of deaths resulting from terrorist attacks (bottom left) by decade. The categories include left-wing extremism, environmental extremism, right-wing extremism, religious extremism, nationalist/separatist extremism, and extremism motivated by a narrowly defined single issue such as opposition to Fidel Castro, opposition to abortion, or opposition to the police.1 One-third (33%) of the attacks were classified as having been motivated by more than one type of ideology; therefore, each column sums to a number (of ideologies) greater than the number of attacks that occurred in each decade. Also note that attacks for which the specific ideological motivation was unknown (24% of all attacks; 2% of all deaths) are not displayed on these graphs.2 In most of the cases for which the ideology of the attacker(s) was unknown it was due to insufficient information about the identity or motivations of the perpetrator, although for some of the cases in which the assailant was unidentified determinations about the ideological motivations of the attack were made based on the identity of the target or anonymous messaging.
Because the variation in both number of attacks and number of deaths by decade make it difficult to see the breakdown of ideologies, the corresponding graphs on the right show the relative frequency, or percentage, of attacks (top) and of deaths that resulted from attacks (bottom). Again, because each attack may have been motivated by more than one type of ideology, the total percentage sums to 100 percent or more.

1970s
In the 1970s the most common ideological motivations for terrorist attacks were left-wing extremism (68% of all attacks and 58% of all deaths) and nationalist/separatist extremism (39% of all attacks and 37% of all deaths). These two categories frequently overlapped as well, as certain nationalist/separatist perpetrator groups tended to adopt a left-wing political perspective. The perpetrator organizations most frequently responsible for left-wing terrorist violence in the 1970s included the New World Liberation Front (NWLF), the Weather Underground, and the Black Liberation Army. Terrorist violence in the 1970s was also frequently attributed to left-wing extremists and black nationalists who were not affiliated with a particular organization.
The Armed Forces of National Liberation (FALN) was the nationalist/separatist perpetrator group responsible for the most attacks in the 1970s. The FALN, along with the Armed Revolutionary Independence Movement (MIRA) and Independent Armed Revolutionary Commandos (CRIA), was a Marxist-Leninist organization that carried out terrorist attacks with the aim of advancing the cause of Puerto Rican independence.
Nationalist/separatist attacks in the 1970s were also attributed to the left-wing Chicano Liberation Front based in Los Angeles and the right-wing, religious organizations the Jewish Defense League (JDL) and its splinter group, the Jewish Armed Resistance (JAR). Other religious perpetrators that were active during the 1970s include the racially motivated “Zebra killers” (a fringe element of the Nation of Islam) and the Ku Klux Klan. Attacks by right-wing extremists in the 1970s also included those attributed to white supremacists and white nationalists who were not affiliated with a particular organization.
There were relatively few attacks in the 1970s motivated by narrowly defined “single issues,” but those that did take place were primarily carried out by perpetrators who opposed the Fidel Castro regime. The most active anti-Castro organizations included Omega-7, the National Front for the Liberation of Cuba (FLNC), and Cuban Action.
1980s
During the 1980s the total number of terrorist attacks in the United States declined by more than 65 percent and the resulting number of victim deaths declined by 70 percent. This shift was largely a result of decreases in violence carried out by the left-wing and nationalist/separatist groups described above. Although certain Puerto Rican independence groups increased their use of violence in the 1980s —including Los Macheteros and the Organization of Volunteers for the Puerto Rican Revolution—they remained far less active than the FALN, which carried out more than 100 attacks in the 1970s and 13 in the 1980s.
Although the number of attacks motivated by a right-wing ideological perspective also declined during this time period, the frequency of right-wing attacks as a proportion of all terrorist violence increased slightly—from 14 percent of all attacks and 19 percent of all victim deaths in the 1970s to 19 percent of all attacks and 48 percent of all victim deaths in the 1980s—due to the more dramatic declines in left-wing and nationalist/separatist violence.
Similar patterns occurred for attacks motivated by religious ideology and single issues. The number of terrorist attacks motivated by religion was stable between the 1970s and the 1980s, but due to the overall decline in terrorism during this time period, the frequency of religiously motivated attacks relative to other types of attacks nearly tripled from 10 percent of all attacks to 29 percent of all attacks. The total number of victim deaths resulting from religiously motivated attacks declined from 40 in the 1970s to nine in the 1980s, comprising 21 percent of victim deaths (down from 26 percent in the 1970s).
Violence motivated by single issues was also relatively stable between the 1970s and the 1980s, but comprised a larger proportion of total terrorist violence in the 1980s (36% of all attacks and 19% of all victim deaths) given the decline in left-wing and nationalist/separatist violence. The specific concerns motivating single-issue violence did shift considerably, however. Attacks by anti-Castro groups and individuals declined from more than 80 in the 1970s to fewer than 50 in the 1980s. Following the legalization of abortion in 1973, the number of attacks motivated by an anti-abortion ideology increased from 10 in the late 1970s to 89 in the 1980s.
1990s
In the 1990s, the total number of terrorist attacks in the United States continued to decline as the use of violence by the Puerto Rican independence movement largely dissipated. Likewise, the 1990s saw decreases in terrorism motivated by left-wing extremism, as well as changes in the specific motivations of left-wing perpetrators. In the
START Background Report ©University of Maryland, November 2017
1970s and 1980s, left-wing perpetrators were most frequently motivated by the goal of Puerto Rican independence, or by anti-war, anti-capitalism, and social justice issues. In comparison, most left-wing terrorist attacks in the 1990s (82%) were carried out by environmentalist groups like the Animal Liberation Front (ALF) and Earth Liberation Front (ELF).3 Terrorism motivated by environmentalism comprised nearly one-quarter (23%) of all attacks in the 1990s, but resulted in no deaths.
The frequency and lethality of right-wing terrorism increased in the 1990s and, like left-wing terrorism, the composition of specific motivations changed as well. The JDL and associated organizations were no longer active perpetrators in the 1990s; however, white supremacist, white nationalist, and anti-government perpetrators became more violent. Most notably, Timothy McVeigh’s April 19, 1995 attack on the Murrah Federal Building in Oklahoma City killed 168 people, injured at least 650 others, destroyed the building, and damaged more than 300 other buildings. This and several other attacks motivated by extreme right-wing ideology caused 89 percent of the deaths that resulted from terrorism in the 1990s.
The frequency and lethality of anti-abortion terrorism also increased in the 1990s. There were 26 percent more anti-abortion terrorist attacks in the 1990s than in the 1980s. While anti-abortion attacks in the 1980s were non-lethal, eight people were killed by perpetrators motivated by opposition to abortion in the 1990s. At least 46 percent of the anti-abortion attacks in the 1990s—including all of the lethal attacks and all of the attacks for which the assailant’s religious identity was specified in source documents—were carried out by perpetrators whose anti-abortion beliefs were rooted in Christianity.4
Terrorism motivated by religious extremism in the 1990s also included attacks perpetrated by Christian Identity groups such as the Aryan Republican Army, the World Church of the Creator, and the Phineas Priesthood. Two anti-Semitic attacks were carried out by Muslim assailants—the 1990 assassination of JDL founder Rabbi Meir Kahane, and a 1994 assault on Jewish students on the Brooklyn Bridge that killed one person and wounded three. Six people were killed and more than 1,000 were injured when Ramzi Yousef detonated a truck bomb in a garage under the World Trade Center in New York in 1993. One of Yousef’s co-conspirators sent a letter to The New York Times claiming responsibility for the attack on behalf of the “Liberation Army Fifth Battalion.” The letter indicated that the attack was carried out in retaliation for the United States’ support for Israel, and warned of future attacks.

2000s
Although the number of terrorist attacks in the United States declined by nearly half in the 2000s, the lethality and long-term impact of al-Qaida’s attacks on September 11, 2001 were extraordinary. Nearly 3,000 people were killed, and thousands more were injured on the day of the attacks. Al-Qaida’s attacks notwithstanding, the 2000s saw a decline in the number of formal perpetrator organizations who were attributed responsibility for terrorist attacks. Although the organizational size, structure, and cohesion varied, more than 30 named groups were responsible for attacks in the 1990s, compared to just eight in the 2000s.5
Other Islamist attacks during the 2000s were primarily carried out by assailants who were not formally affiliated with particular perpetrator organizations. These include Nidal Hasan’s 2009 attack at Fort Hood in Texas, in which 13 people were killed and more than 30 others were injured. Although lethal terrorist attacks motivated by Christian, anti-abortion ideology and anti-Semitic ideology also took place in the 2000s, there were far fewer than had occurred in the 1990s.

The number of attacks by left-wing extremists increased 80 percent in the 2000s. These attacks were nearly all motivated by environmentalism and carried out by perpetrators affiliated with ALF and ELF. All of these attacks were intended to cause property damage and intimidation; none were lethal. The number of attacks motivated by right-wing extremism declined by 40 percent between the 1990s and the 2000s, and included attacks carried out by perpetrators motivated by white supremacy and neo-Nazi ideology, as well as anti-Semitism, anti-immigration, and anti-abortion beliefs, and opposition to progressive social policies.

2010s
In comparison to the 2000s, there was a sharp decline in the proportion of terrorist attacks carried out by left-wing, environmentalist extremists during the first seven years of the 2010s (from 64% to 12%). At the same time, there was a sharp increase in the proportion of attacks carried out by right-wing extremists (from 6% to 35%) and religious extremists (from 9% to 53%) in the United States.

Terrorist attacks attributed to formal organizations remained relatively rare. Instead, attacks between 2010 and 2016 were typically carried out by individual perpetrators who were only loosely linked to a specific organization or ideological movement. The motivations for attacks were both diverse and overlapping. In some cases they were narrowly focused on issues and in other cases inspired by broad belief systems. They included both oppositional (anti-) and affirmative (pro-) views, or sometimes both.
The lethality of terrorism in the United States between 1970 and 2016 was characterized by thousands of non-lethal attacks (91%) that were punctuated by relatively rare but deadly, or even exceptionally deadly, attacks. Although the lethality of attacks during the 2010 to 2016 time period did not nearly match that of the two prior decades, this basic pattern remained. For example, of the 68 people killed in attacks carried out by jihadi-inspired extremists during this period, 49 died in Orlando, Florida as a result of a 2016 armed assault carried out by Omar Mateen. Fourteen others died in San Bernardino, California in a 2015 attack by Syed Farook and Tashfeen Malik. Likewise, nine of the 18 people killed by white supremacists or white nationalists died as a result of Dylann Roof’s 2015 attack at Emanuel African Methodist Episcopal Church in Charleston, South Carolina. Six others were killed when Wade Michael Page attacked worshippers at a Sikh temple in Oak Creek, Wisconsin. This demonstrates that the overall trends in terrorism in the United States with respect to ideology are highly sensitive to the influence of individual mass-casualty attacks.

APPENDIX: IDEOLOGY DEFINITIONS
Left-wing extremism
Violence in support of a revolutionary socialist agenda and the view that one is a protector of the populace. Characterized by disdain for capitalism, imperialism, and colonialism, and by a Marxist political focus and pro-communist/socialist beliefs, or support for a decentralized, non-hierarchical sociopolitical system (e.g., anarchism).
Environmental extremism
Violence in support of biodiversity and bio-centric equality (the view that humans have no legitimate claim to dominate earth). Characterized by the belief that the earth and/or animals are in imminent danger, that the government and parts of society such as corporations are responsible for this danger, that this danger will ultimately result in the destruction of the modern environment and/or whole species, and that the political system is incapable and/or unwilling take action to preserve the environment, and/or support biological diversity.
Right-wing extremism
Violence in support of the belief that personal and/or national way of life is under attack and is either already lost or that the threat is imminent. Characterized by anti-globalism, racial or ethnic supremacy or nationalism, suspicion of centralized federal authority, reverence for individual liberty, and/or belief in conspiracy theories that involve grave threat to national sovereignty and/or personal liberty.
Religious extremism
Violence in support of a particular faith-based belief system and its corresponding cultural practices and views, sometimes in opposition to competing belief systems. Characterized by opposition to purported enemies of God, nonbelievers, or perceived evildoers; striving to forcibly insert religion into the political or social sphere through the imposition of strict religious tenets or laws; and/or bring about end times. (Subcategories: Christian, Jewish, Islamic)
Nationalist/separatist extremism
Violence in support of ethnic or geo-political self-determination. Characterized by regional concentration and a history of organized political autonomy, traditional rule, or regional government, and a commitment to gaining or regaining political independence.
Single-issue extremism
Violence in support of advancing a specific or narrowly defined cause. This belief may be associated with any space on the political spectrum.