On Sunday, Aug. 27, a “rally against hate” was scheduled in Berkeley, California, by a small group of relatively conservative Christians, led by Amber Cummings, a transgender Trump supporter and a leader of a group called Patriot Prayer, and a Japanese-American named Joey Gibson.

Their event never took place. The left-wing group known as antifa, a contraction of “anti-fascist,” showed up in large numbers. Videos shows its members pouncing on one of the rally supporters, knocking him to the ground, and preparing to beat him with sticks and rocks. The Washington Post reported:

“A pepper-spray-wielding Trump supporter was smacked to the ground with homemade shields. Another was attacked by five black-clad antifa members, each windmilling kicks and punches into a man desperately trying to protect himself. A conservative group leader retreated for safety behind a line of riot police as marchers chucked water bottles, shot off pepper spray and screamed, ‘Fascist go home!’”

There’s no consensus of what antifa stands for, or if their tactics will achieve their stated goals. Is it, as leftist professor Todd Gitlin asserts, simply a “particular strand of aggressive left-wing activism,” that is a “defensive response to the growing presence of right-wing extremism,” or is it, as liberal editor and columnist Josh Marshall writes, a group which empowers “violence over law… the surest route to the destruction of democracy and dictatorship?”

Many trace the group’s origins back to the antifascists who fought Mussolini in 1920’s Italy and the communist action groups that engaged in street fighting with Hitler’s SA Brownshirts in the early 1930s in Weimar Germany. Indeed, antifa’s ultimate justification for their use of violence is that era. Resistance, historian Mark Bray argued in The Washington Post, should “simply be flipped on in a crisis. Once the Nazi and fascist parties gained control of government, it was too late to pull the emergency brake.”

Writing in The Nation, antifa activist Natasha Lennard urges liberals not to criticize them for being “willing to put their bodies on the line against neo-Nazis.” Seeing fascism in the U.S. “in Trump’s ascendance,” Lennard eschews “polite protest,” favoring in its place making sure that “all far-right events will be bombarded and besieged.”

Comparing herself and her comrades directly to “the international militant brigades fighting Franco in Spain, the Red Front Fighters’ League in Germany who were fighting Nazis since the party’s formation in the 1920s,” and the members of the “43 Group in England fighting Oswald Mosley’s British Union of Fascists” in street brawls in London, she emphasizes that they all depended upon “physical combat.”

That call to violence—somehow supposedly defensive even when the antifas initiate it—leaves little to discuss with moderate liberals like Peter Beinart, Todd Gitlin, Devin Foley, and the editors of The Washington Post. A widely circulated call to arms on the anarchist site “It’s Going Down” in December dismissed union leaders, politicians of the left, and NGOs, declaring that the only thing stopping Trump’s march to fascism was “the blockaders. The people in ski masks and in the streets. The ones on the front lines fighting with cops. The people attacking, defending, organizing, building, and growing.”

As Josh Meyer reported in Politico, back in early 2016, the FBI warned during the Obama presidency that antifa, composed of “anarchist extremists,” had become confrontational and dangerous and were often the main instigators of violence at public rallies. Both sides now come to announced events ready for violent confrontation. The bureau noted a June 2016 rally in Sacramento where antifa groups caused “a riot after which at least 10 people were hospitalized, some with stab wounds.”

Antifa’s attitude is the same taken by the German Communist Party (KPD) before Hitler’s ascension to power. The German Reds had the slogan “After Hitler, Us,” and used their energy and propaganda not against the Nazis, but against the mainstream socialists, organized in the Social-Democratic Party (SPD).

Calling the SPD “social fascists,” the Communists argued that to give them any credibility would fool the working classes into supporting them when in fact the SPD’s opposition to an immediate communist revolution meant that the Nazis would win power. Despite pleas of many on the left, including Leon Trotsky, who had fled to Mexico to escape Stalin’s henchmen, the KPD leadership refused to join in a united front against the Nazi Party, and even voted with the Nazis against seats in the Prussian parliament for any German Socialist Party members.

Bray knows this, and writes that “while Hitler was planning a war against the Left, socialists and communists focused on fighting each other.” Indeed, as he acknowledges, communist leaders called the Social-Democrats fascists “with a socialist phraseology.” Yet he argues that now, in the Trump era, what is needed are “street confrontations” since—as in the 1930s—“the liberal playbook for stopping the advance of fascism failed.”

Despite this history, today’s antifa—which takes the name from the KPD’s street fighting group established in 1932, Antifaschitische Aktion—acts the same way toward centrists and liberals who reject their commitment to violence. Its members have also frequently assaulted photographers and members of the press seeking to document their public violence.

It should be apparent, but evidently is not to antifa members and leaders, that the United States, despite Donald Trump being president, is not in a comparable situation to that of Weimar Germany on the eve of Hitler’s ascension to power, or to Nazi Germany after the passage of the Enabling Act, which in 1933 gave Hitler the power to pass laws without the participation of the Reichstag. After this, Hitler and the Nazi Party assumed total control and established a one-party state without any political liberties.

Antifa members should read historians of Nazi Germany, like Laurie Marhoefer of the University of Washington, who writes that anti-fascist street fighters who greeted a Nazi rally with violence thought that they had won by disrupting a rally and fighting its speakers back in 1927. They sent a message that “Fascism was not welcome.” But instead, “events like the rally in Wedding [a Berlin district] helped the Nazis build a dictatorship.” The Reds got media attention, but it led to escalating street violence, all of which helped the Nazis, who painted themselves “as the victims of a pugnacious, lawless left.”

Leftist violence in the 1930s in Germany led many to support the Nazis in the hope they would put an end to the continuing street brawls and violence. Today, the antifa left may even help to get Donald Trump reelected in 2020.