What is extremism? A starting point is recognizing that the term only becomes meaningful within a specific historical context and relative to other movements. Liberal democracy, women’s suffrage, and nationalism, just to take three examples, were once “extreme” but have become commonplace, even expected. Therefore, whenever the word “extreme” is applied to a given actor or ideology we must ask: extreme as compared to what and, most importantly, when and where?

Another problem with labeling a movement as extreme is that it can quickly become reductive. “Extreme” movements are rarely homogenous and indeed are usually rich in complexities, paradoxes, and nuances. But all too often “extremists” are reduced to caricatures.

This is particularly true when extremism is accompanied by violence, even in relatively limited ways and by only a small subset of proponents. The violence of an extremist movement can lead observers to confuse what might simply be one aspect of the movement – in this case, violence – with the whole, thus tainting all adherents as physically threatening. And this can lead to real-world consequences.

A good example is the history of anarchist violence. Anarchism emerged as a vibrant but disconcerting ideology in the middle of the nineteenth century. Anarchists – like socialists – denounced the dehumanizing impact of capitalism and the exploitation of workers by factory owners. But whereas most socialists eventually advocated for more worker control or influence over the state, anarchists saw the state itself as the problem. Therefore, anarchists demanded the abolition of government and the creation of self-governing communes and societies. While anarchists typically spoke of “revolution,” most were pacifists who denounced violence.

But a vocal minority of anarchists came to believe that only violence could force entrenched bourgeois interests to relinquish their power and turned to terrorism. In the 1870s and early ’80s, this mostly took the form of targeted assassinations of prominent political figures, military leaders, and industrialists. Prominent examples were the failed attempts on the German emperor Wilhelm I and the Italian king Umberto I in 1878. These attempts accomplished nothing in terms of directly advancing the anarchist agenda, but that was beside the point.

This brings us to terrorism, which had emerged by the 19th century as a distinct strategy that uses symbolic violence against a few to influence the behavior of the many. In a famous anarchist phrase of the period, terrorism functions as “propaganda of the deed,” meaning that the act itself rouses people to action as a piece of wordless communication by terrifying or provoking one audience (the government, for instance, or the bourgeoisie), while it excites or encourages another (workers, for example).

This explanation should make clear that terrorism is a strategy and not itself an ideology. Terrorism can and has been used by nationalists, anarchists, democrats, socialists – which is to say by adherents of nearly every “ism” under the sun.

Terrorism is a “hail Mary” pass – a way to achieve indirectly that which cannot be achieved directly. In other words, terrorism is typically used by those who do not have the means – in terms of supporters, money, votes, or weapons – to pursue more conventional or moderate strategies to achieve their goals. And this also means that while those who use terrorism are often able to terrify or intimidate, they are not often capable of ultimately winning. And this means that the real threat they pose is wildly disproportionate to the fear they generate – which is exactly what terrorists want to do and why they use the strategy that they use.

This is the context in which we must evaluate the “extremist” anarchists of the late 19th and early 20th centuries. One could say that they failed as terrorists since their violence trumped their message. Indeed, their violence became their message since much of society saw terrorism as their sole defining characteristic. In fact, conservatives and moderates viewed any leftist ideology as interchangeably “extreme,” violent, and dangerous, and this played into the hands of those with ulterior motives. In Germany, Chancellor Otto von Bismarck deliberately used society’s great fear of terrorist violence to pressure the German legislature into passing a series of anti-socialist bills. Bismarck then used them to arrest leaders, shutter newspapers, and limit the work of the Social Democratic Party of Germany (the SPD), Europe’s largest socialist party, which was, unlike the anarchists, a very real threat to the political and economic elite of the country.

Bismarck’s efforts generally failed, but they further obfuscated the distinctions between varieties of leftism, between leftist ideologies and terrorism, and between ideologies and the violence occasionally used to advance them. And his disingenuous anti-socialist laws launched Germany on a long-term quixotic quest to marginalize socialism, which limited the expansion of economic and political rights. Moreover, Bismarck’s actions exacerbated economic and political tensions that contributed to Imperial Germany’s collapse at the end of World War I.

Meanwhile, in the late 1880s and ’90s, violent anarchists began to expand their use of terrorism by expanding how they conceptualized symbolic targets, in particular by going after civilians and public places in some of the modern world’s first mass-casualty terrorist attacks. In the mid-1890s, several individual anarchists each acting alone terrorized Paris in a series of bombings of cafes and other public meeting areas of the bourgeoisie. In Barcelona, anarchists threw bombs in churches and at religious processionals. Anarchists also stepped up their attacks on political leaders, assassinating French President Sadi Carnot in 1894 and U.S. President William McKinley in 1901. The culmination of anarchist terrorism came in the United States in 1917-20 when a small cell carried out a campaign of postal bombings and detonated a carriage full of explosives on Wall Street.

While anarchist terrorism never rose to the level of existential threat since it caused relatively few casualties and never represented the will of more than a fringe of the left, it provoked the American government into engaging in dangerous and deeply consequential actions. Even though anarchism’s libertarian and anti-authoritarian impulses meant that it was quite compatible with much of the American experience, most Americans saw it as deeply alien. This was in large part because it was so closely associated with the labor movement, which owed much of its size and influence to the influx of millions of newly-arrived immigrants. Therefore, anarchism and terrorism became synonymous with immigrants themselves. In politicians’ speeches, popular journalistic accounts, and widely disseminated political cartoons, the anarcho-terrorist was essentialized and depicted as a crazed, bearded foreigner clutching a knife or hiding a bomb under his overcoat. The American fear – both genuine and manipulated – of the foreign anarchist-cum-terrorist became so pervasive that it led to legislation that demonized the already marginalized, curtailed foreign immigration, and undermined civil liberties. It also distracted Americans from far more pervasive, pernicious, consequential, and – not surprisingly native – forms of terrorism, namely white supremacist violence.

None of this is to say that terrorism is benign or that states shouldn’t act to protect their people from violence. The danger is that extremism, particularly violent extremism, can all too easily be fundamentally misread or deliberately manipulated. In the case of anarchism and anarchist violence in the late 19th and early 20th centuries, this caused deep and lasting harm to American and European societies and their values.