On October 4, 1936, tens of thousands of Zionists, Socialists, Irish dockworkers, Communists, anarchists, and various outraged residents of London’s East End gathered to prevent Oswald Mosley and his British Union of Fascists from marching through their neighborhood. This clash would eventually be known as the Battle of Cable Street: protesters formed a blockade and beat back some three thousand Fascist Black Shirts and six thousand police officers. To stop the march, the protesters exploded homemade bombs, threw marbles at the feet of police horses, and turned over a burning lorry. They rained down a fusillade of projectiles on the marchers and the police attempting to protect them: rocks, brickbats, shaken-up lemonade bottles, and the contents of chamber pots. Mosley and his men were forced to retreat.

In “Antifa: The Anti-Fascist Handbook,” published last week by Melville House, the historian Mark Bray presents the Battle of Cable Street as a potent symbol of how to stop Fascism: a strong, unified coalition outnumbered and humiliated Fascists to such an extent that their movement fizzled. For many members of contemporary anti-Fascist groups, the incident remains central to their mythology, a kind of North Star in the fight against Fascism and white supremacy across Europe and, increasingly, the United States. According to Bray, Antifa (pronounced an-tee-fah) “can variously be described as a kind of ideology, an identity, a tendency or milieu, or an activity of self-defense.” It’s a leaderless, horizontal movement whose roots lie in various leftist causes—Communism, anarchism, Socialism, anti-racism. The movement’s profile has surged since Antifa activists engaged in a wave of property destruction during Donald Trump’s Inauguration—when one masked figure famously punched the white supremacist Richard Spencer in the face—and ahead of a planned appearance, in February, by Milo Yiannopoulos at the University of California, Berkeley, which was cancelled. At the “Unite the Right” rally in Charlottesville, Virginia, a number of Antifa activists, carrying sticks, blocked entrances to Emancipation Park, where white supremacists planned to gather. Fights broke out; some Antifa activists reportedly sprayed chemicals and threw paint-filled balloons. Multiple clergy members credited activists with saving their lives. Fox News reported that a White House petition urging that Antifa be labelled a terrorist organization had received more than a hundred thousand signatures.

Bray’s book is many things: the first English-language transnational history of Antifa, a how-to for would-be activists, and a record of advice from anti-Fascist organizers past and present—a project that he calls “history, politics, and theory on the run.” Antifa activists don’t often speak to the media, but Bray is a former Occupy Wall Street organizer and an avowed leftist; he has intimate access to his subjects, if not much critical distance from them. Especially in later chapters of the book, that access helps him to provide an unusually informed account of how Antifa members conceptualize their disruptive and sometimes violent methods.

Many liberals who are broadly sympathetic to the goals of Antifa criticize the movement for its illiberal tactics. In the latest issue of The Atlantic, Peter Beinart, citing a series of incidents in Portland, Oregon, writes, “The people preventing Republicans from safely assembling on the streets of Portland may consider themselves fierce opponents of the authoritarianism growing on the American right. In truth, however, they are its unlikeliest allies.” (Beinart’s piece is headlined “The Rise of the Violent Left.”) According to Bray, though, Antifa activists believe that Fascists forfeit their rights to speak and assemble when they deny those same rights to others through violence and intimidation. For instance, last week, the North Dakota newspaper The Forum published a letter from Pearce Tefft in which he recalled a chilling exchange about free speech with his son, Peter, shortly before Peter headed to the rally in Charlottesville. “The thing about us fascists is, it’s not that we don’t believe in freedom of speech,” the younger Tefft reportedly said to his father. “You can say whatever you want. We’ll just throw you in an oven.”

For Bray and his subjects, the horror of this history and the threat of its return demands that citizens, in the absence of state suppression of Fascism, take action themselves. Bray notes that state-based protections failed in Italy and Germany, where Fascists were able to take over governments through legal rather than revolutionary means—much as the alt-right frames its activities as a defense of free speech, Fascists were able to spread their ideology under the aegis of liberal tolerance. Antifa does not abide by John Milton’s dictum that, “in a free and open encounter,” truthful ideas will prevail. “After Auschwitz and Treblinka,” Bray writes, “anti-fascists committed themselves to fighting to the death the ability of organized Nazis to say anything.”

Part of Antifa’s mission is to establish, as Bray puts it, “the historical continuity between different eras of far-right violence and the many forms of collective self-defense that it has necessitated across the globe over the past century.” To this end, the first half of his book is a somewhat rushed history of anti-Fascist groups. The progenitors of Antifa, in this account, were the German and Italian leftists who, following the First World War, banded together to fight proto-Fascist gangs. In Italy, these leftists gathered under the banner of Arditi del Popolo (“the People’s Daring Ones”), while in Weimar Germany, groups like Antifaschistische Aktion, from which Antifa takes its name, evolved from paramilitary factions of existing political parties. Bray moves swiftly to the failure of anti-Fascists in the Spanish Civil War, then races through the second half of the twentieth century. In the late seventies, the punk and hardcore scenes became the primary sites of open conflict between leftists and neo-Nazis; that milieu prefigures much of the style and strategy now associated with the anti-Fascist movement. In the Netherlands and Germany, a group of leftist squatters known as Autonomen pioneered the Black Bloc approach: wearing all-black outfits and masks to help participants evade prosecution and retaliation. Bray reaches the present with his description of “Pinstripe Fascists,” such as Geert Wilders, and the rise of new far-right parties and groups in both Europe and America. The book flits between countries and across decades; analysis is sparse. The message is that Antifa will fight Fascists wherever they appear, and by any means necessary.

The book’s later chapters, such as “Five Historical Lessons for Anti-Fascists” and “ ‘So Much for the Tolerant Left!’: ‘No Platform’ and Free Speech,” which are adapted from essays published elsewhere, are more focussed and persuasive. Here Bray explicitly deals with the philosophical and practical problems of Antifa: violence versus nonviolence; mass movements versus militancy; choosing targets and changing tactics. Bray concedes that the practice of disrupting Fascist rallies and events could be construed as a violation of the right to free speech and assembly—but he contends that such protections are meant to prevent the government from arresting citizens, not to prevent citizens from disrupting one another’s speech. Speech is already curtailed in the U.S. by laws related to “obscenity, incitement to violence, copyright infringement, press censorship during wartime,” and “restrictions for the incarcerated,” Bray points out. Why not add one more restriction—curtailing hate speech—as many European democracies do? As for the slippery-slopists, afraid that Antifa will begin with Fascists and eventually attack anybody who opposes them, Bray maintains that the historical record does not support this fear: anti-Fascists who have shut down local hate groups, as in Denmark, usually go dark themselves, or turn their attention to other political projects, rather than finding new enemies to fight. (In his Atlantic piece, Beinart notes, “When fascism withered after World War II, antifa did too.”)

Violence, Bray insists, is not the preferred method for past or present Antifa—but it is definitely on the table. He quotes a Baltimore-based activist who goes by the name Murray to explain the movement’s outlook: