In its online salvo against antifa and “far-left mobs,” President Trump’s reelection campaign displayed a marking the Nazis once used to designate political prisoners in concentration camps.

A red inverted triangle was first used in the 1930s to identify Communists, and was applied as well to Social Democrats, liberals, Freemasons and other members of opposition parties. The badge forced on Jewish political prisoners, by contrast, featured a yellow triangle overlaid by a red triangle.

In response to queries from The Washington Post, Facebook on Thursday afternoon deactivated ads that included the inverted red triangle.

The red symbol appeared in paid posts sponsored by Trump and Vice President Pence, as well as by the “Team Trump” campaign page. It was featured alongside text warning of “Dangerous MOBS of far-left groups” and asking users to sign a petition about antifa, a loose collection of anti-fascist activists whom the Trump administration has sought to link to recent violence, despite arrest records that show their involvement is trivial.

“We removed these posts and ads for violating our policy against organized hate,” said Andy Stone, a Facebook spokesman. "Our policy prohibits using a banned hate group’s symbol to identify political prisoners without the context that condemns or discusses the symbol.”

But the ads on the president’s page alone, which began running on Wednesday, gained as many as 950,000 impressions by Thursday morning. Identical ads on Pence’s page gained as many as 500,000 impressions.

Tim Murtaugh, a spokesman for the Trump campaign, said, “The red triangle is an antifa symbol,” pointing to examples of iPhone cases and water bottles branded with the insignia. A more common emblem for the anti-fascist movement includes two flags, one red and one black, enclosed in a circle.

Although certain symbols the Nazis deployed have been reclaimed, including the pink triangle used in concentration camps to label gay inmates, the red triangle has not been recast in a similar way, said Jacob S. Eder, a historian of modern Germany at the Barenboim–Said Akademie in Berlin.

“I think it’s a highly problematic use of a symbol that the Nazis used to identify their political enemies,” he said. “It’s hard to imagine it’s done on purpose, because I’m not sure if the vast majority of Americans know or understand the sign, but it’s very, very careless, to say the least.”

Deborah E. Lipstadt, a leading American scholar of the Holocaust, said the inclusion of the symbol in alarmist advertising bore echoes of the campaign’s initial decision to hold a rally in Tulsa on June 19, known as Juneteenth in commemoration of the end of slavery. Trump delayed the rally by a day following an outcry.

“It’s an insensitivity, and likely indicative of who’s around the table when these decisions are being made,” she said. “I find it shocking.”

Murtaugh, the Trump campaign spokesman, noted that the marking is not included in the Anti-Defamation League’s database of hate symbols. But the ADL’s CEO, Jonathan Greenblatt, condemned its use in political combat as “offensive and deeply troubling.”

“It is not difficult for one to criticize their political opponent without using Nazi-era imagery,” Greenblatt said in a statement. “We implore the Trump campaign to take greater caution and familiarize themselves with the historical context before doing so. Ignorance is not an excuse for appropriating hateful symbols.”

Jake Hyman, an ADL spokesman, said the marking is not in the organization’s hate database because the inventory is not for “historical Nazi symbols" but rather for “symbols commonly used by modern extremists and white supremacists in the United States.”

Bend the Arc: Jewish Action, a progressive advocacy group, also condemned the use of the notorious symbol in campaign advertising.

“This isn’t just one post,” the group wrote on Twitter. “This is dozens of carefully targeted ads from the official pages of Mike Pence, Donald Trump, and Team Trump. All paid for by Trump and the Republican National Committee. All spreading lies and genocidal imagery.”

Eighty-eight ads with the inverted red triangle ran in total — across pages for Trump, Pence and the official “Team Trump” page on the social network.

Variations of the ad used a yield sign, which has the same shape and a similar color scheme but is notably distinct in featuring only a red outline and a white interior. Some of the material also featured a stop sign.

Trump has made antifa — a label associated with anti-fascist protesters who infamously sparred with far-right figures after his election in 2016 — a centerpiece of his response to recent demonstrations in the aftermath of the killing of George Floyd in police custody in Minneapolis. The effort to rally his supporters using the specter of a marauding horde resembles the emphasis he placed on the threat of a migrant caravan heading to the U.S. border in the lead-up to the midterm election in 2018.

So far, however, the alleged menace has been mostly nonexistent — a focal point of online alarm not reflected in scenes of mostly peaceful protest nationwide. Despite warnings of antifa incursions in scores of cities, there is no evidence linking outbursts of violence to an organized left-wing effort.

During the 2016 campaign, Trump tweeted, and then deleted, a graphic showing Hillary Clinton alongside $100 bills and a six-pointed Star of David — the type of star that the Nazis forced Jews to wear on their clothing. The then-candidate insisted in a statement that the insignia was not anti-Semitic because it represented a sheriff’s badge, not the stigmatized Star of David.