In October of 1936, as news broke of Franco’s rise in Spain, roughly 100,000 demonstrators gathered in the streets of London’s predominantly Jewish East End to counterprotest a British Union of Fascists march. The police beat back crowds of mostly Jewish and Irish residents to make way for Oswald Mosley, the British Union of Fascists’ leader, who wanted to spread the gospel of fascism to Britain. On Cable Street, fascists and anti-fascists were facing off. Fascists alternated between chanting, “The Yids, the Yids, we are going to get rid of the Yids” and “We want free speech!” In response, anti-fascist demonstrators turned over a truck, mattresses, and furniture to block the road. When police charged at them, they threw boxes of gunpowder. It would become known as the Battle of Cable Street. The result: Oswald Mosley called the march off. Deliberate violence had beaten the fascists back.

For as long as there have been fascists, there has been debate over the way to respond to them. In his new book, Antifa, historian and organizer Mark Bray traces various leftist anti-fascist movements from the 1930s Europe to the “Antifa” movements we see on the streets today. The history of anti-fascism, it seems, is stuck on repeat, with the same arguments over free speech and uncompromising resistance cropping up repeatedly.

Disruption—sometimes violent disruption—has been central to anti-fascist action from the beginning. Many Jewish anti-fascists in Britain argued, “fists can be put to better service than propelling pens.” Communist anti-fascist papers in Germany read, “Hit the fascists wherever you meet them!” and “Wherever a fascist dares to show his face in the quarters of the working class, workers’ fists will light his way home. Berlin is red! Berlin is staying red!”

But others were quick to rebuff these tactics. After the Battle of Cable Street, the older Jewish generation argued that the anti-fascists were “copying the Nazi violence which we loathe and detest.” They thought Jews should take the moral high ground and “show the world that the Jew can be as good a citizen as anybody else.” Some political groups issued leaflets arguing for “Dignity, Order, and Discipline.” Rather than facing off with the fascists, those who opposed fascism should attend a rally in support of the Spanish Republic nearby instead, they argued. Fascism could be quashed through legal and electoral means.

One of the reasons the debate over the use of violence against fascism is difficult to resolve is that fascism itself is difficult to define. Bray describes it as “a form of political behavior marked by obsessive preoccupation with community decline, humiliation, or victimhood and by compensatory cults of unity, energy, and purity, in which a mass-based party of committed nationalist militants, working in uneasy but effective collaboration with traditional elites, abandons democratic liberties and pursues with redemptive violence and without ethical or legal restraints goals of internal cleansing and external expansion.”

Fascism, it seems, is more easily identified in retrospect. As Eric A. Johnson and Karl Heinz Reuband explained in their book about Nazism, What We Knew, “far from living in a constant state of fear and discontent, most Germans led happy and even normal lives in Nazi Germany … most tell us that they did not fear being arrested.”

The problem is that you can’t resist fascism in retrospect, so the anti-fascist response throughout history has taken as many forms as the fascist forces it opposes. Bray defines anti-fascism as an organizing strategy, not a group of people, “a model of resistance” undergirded by an understanding of fascism’s history: “anti-fascists have concluded that since the future is unwritten, and fascism often emerges out of small, marginal groups, every fascist or white-supremacist group should be treated as if they could be Mussolini’s one hundred Fasci.” There is no leadership, no spokesperson, no single headquarters. Many disparate groups have ascribed to anti-fascist ideology from the anti-Faschistische Aktion of Weimar Germany, and Comité d’Action anti-Fasciste in France, to the Jewish veterans’ Ex-Servicemen’s Movement Against Fascism in England.

When anti-fascists in Germany began defacing Nazi flags, the entrenched leadership argued against it on the grounds that it was illegal, “We shall make ourselves ridiculous with all this nonsense,” they said. This defacement — three downward arrows painted over the swastika — would become the anti-fascist flag that is still widely used today.

In the case of pre-WWII Europe, the condoned legal channels proved entirely ineffective in halting the tide of fascism. As Bray explains, “the traditional right thought they could control Hitler by bringing him into government.” While Hitler himself suggested that opposition to the Nazis failed because opponents couldn’t understand what the Nazis were actually doing.

Protest has always been inextricably linked to questions of free speech. But as Bray demonstrates, the most effective fascist movements seek to grow their support base by taking on more palatable mantles. Overtly xenophobic messaging doesn’t appeal to everyone, but rights discussions are something more people can get behind. (Sound familiar?)

Of course, critics of violent anti-fascism are correct in arguing that violent actions can inspire a backlash that accelerates fascism. As Bray points out, three separate assassination attempts on Mussolini’s life “were used to eliminate all non-fascist political parties and journals, thereby inaugurating Mussolini’s dictatorship.” (Though it’s worth noting that none of these attempts were claimed by anti-fascist groups).

Perhaps no one knows better how to beat fascism than a fascist himself. Looking back on the Nazi rise to power, Hitler suggested that it could have only been stopped if opposition forces “had from the first day annihilated with the utmost brutality the nucleus of our new movement.” There was a window of opportunity for their destruction — and it was early. Like all movements, fascism in Europe during this period began small. In 1919, Mussolini had only 100 supporters. And as Goebbels said, “If the enemy had known how weak we were, it would probably have reduced us to jelly…. It would have crushed in blood the very beginning of our work.”