President Trump is blaming a radical leftist group for organizing violent protests and attacks on police. Is this true? Here's everything you need to know:

What is antifa?
It's an umbrella movement of leftists and anti-racists, rather than an actual group. Antifa (pronounced an-TEE-fa by some, anti-FAH by others) adherents see their mission as using direct action, up to and including violence, to fight fascism and the "alt-right." They believe that law enforcement is complicit in white supremacy, and that democracy is in danger. The term had its origins in the anti-fascist groups that sprang up in Germany and the U.K. in the 1930s, and members believe that the Nazis would not have been able to take power in Germany if anti-fascists had fought them aggressively. The first American group to use the term was the Rose City Antifa in Portland, Oregon, in 2007. Because there is no leadership, hierarchy, or organized recruitment, anyone can call themselves antifa. "It's like calling Deadheads or Red Sox Nation" an organization, said Brian Levin, director of the Center for the Study of Hate and Extremism at California State University, San Bernardino. It's unclear how many people identify as antifa, but it's probably a few thousand at most; it is certain that they make up only a tiny fraction of the hundreds of thousands of Americans who have been demonstrating in more than 100 cities against the killing of George Floyd. Nonetheless, Attorney General William Barr has blamed "antifa and other similar extremist groups" for "hijacking" the protests to instigate violence.

Has antifa been violent in the past?
Yes, at times. Most antifa activists, says Mark Bray, a history professor and author of Antifa: The Anti-Fascist Handbook, focus on trying to identify the names, addresses, and jobs of white supremacists who are active on the internet, and "outing" them to their employers and the public. "It's a lot of a kind of private investigator work that sometimes spills out into the streets with confrontations," Bray said. Still, there have been violent attacks. In 2012, militants from Anti-Racist Action, loosely associated with antifa, stormed a Chicago-area restaurant where a white-supremacist group was meeting, attacking with baseball bats and hammers and injuring several people; five of them pleaded guilty to armed violence. After President Trump's inauguration in 2017, a masked activist punched white nationalist Richard Spencer in the face. The next month, a group of some 150 masked, black-clad activists interrupted what had been a peaceful protest against an appearance by right-wing provocateur Milo Yiannopoulos in Berkeley, California, throwing fireworks, smashing windows, and hurling rocks. Later that year, antifa activists battled white supremacists in Charlottesville, Virginia.

What happened in Charlottesville?
Hundreds of counter-protesters, including some who identify as antifa, showed up at a Unite the Right white-supremacist rally in August 2017. Witnesses there, including Jewish and Christian clergy, say that they were being physically threatened by neo-Nazis wielding semi-automatic rifles, clubs, and torches when antifa members inserted their own bodies as shields. Fistfights and mace-spraying broke out. One neo-Nazi was convicted of homicide when he rammed his car into a crowd, killing protester Heather Heyer, 32. "We would have been crushed like cockroaches if it were not for the anarchists and the anti-fascists," said activist and Harvard professor Cornel West.

What about Barr's allegations?
Internal FBI documents leaked to The Nation show that the FBI's Washington field office "has no intelligence indicating antifa involvement/presence" in the D.C.-area protests. In other areas, experts say antifa is simply too small a presence to be a driving force in protests. Witnesses have said they saw both black-clad militant activists who could be antifa and white-supremacist agitators breaking windows and starting fires, but records show that the vast majority of those arrested were from local communities. Many looters, police said, were professional criminals.

What has President Trump said?
He's blamed "antifa-led anarchists" for violent protests and has vowed to designate antifa as a "terrorist organization." Under U.S. law, however, only foreign actors such as al Qaeda or the Irish Republican Army can be so defined. Critics have accused Trump and Barr of focusing on antifa as an excuse to invoke the Insurrection Act, call out the military, and put U.S. soldiers on the streets of American cities. Writing in The New York Times last week, Sen. Tom Cotton (R-Ark.) called for "an overwhelming show of force" against "cadres of left-wing radicals like antifa infiltrating protest marches."

Is antifa active on social media?
Since Floyd's killing, Twitter and Facebook have taken down what Twitter called "hundreds of spammy accounts," many purporting to be antifa and calling for violence against police or white neighborhoods. Several of those have been traced to the white-supremacist groups Identity Evropa, Proud Boys, and American Guard. On Facebook over the past week, rumors of imminent antifa attacks and riots in small towns and suburbs have put local law enforcement on alert; the attacks never materialized. "I don't think there was any truth to it," said John Lane, chief of police in East Liverpool, Ohio, who put on extra patrols after a Facebook page attributed to antifa threatened a suburban riot. "But I think this is going to go on until Election Day."

The Boogaloo movement
Boogaloo — which takes its name from the ridiculously titled 1984 movie sequel Breakin' 2: Electric Boogaloo — is a loosely organized, far-right movement that includes gun enthusiasts and white supremacists who say they want to trigger a race war that will bring down the U.S. government. Like antifa, there are no formal leaders or organization, and most of the action seems to take place online. But many Boogaloo followers have appeared at COVID-19 lockdown protests, armed and wearing Hawaiian shirts, and some have now begun showing up at the ongoing protests against police brutality. In recent years, police say they have foiled several domestic terrorist plots by those claiming to follow the ideology. Last week, three ex-military men who police say self-identify as Boogaloo Bois were arrested on the way to a Las Vegas Black Lives Matter protest with full gas cans and Molotov cocktails in their car.

This article was first published in the latest issue of The Week magazine. If you want to read more like it, you can try six risk-free issues of the magazine here.