During Donald Trump’s campaign for president, the Anti-Defamation League, a nonprofit dedicated to fighting anti-Semitism and other forms of bigotry, asked him to stop using the phrase “America First” to describe his foreign policy views. As the ADL explained, the slogan was used by people who warned, ahead of World War II, that Jewish Americans were pushing the U.S. to enter the war because they put their own interests ahead of the country’s.

But Trump never stopped using the slogan. And on Friday, he made it a key part of his inaugural address. “From this day forward,” he proclaimed, “A new vision will govern our land. From this moment on, it’s going to be America First.”

The crowd went wild.

People who aren’t Jewish or familiar with the history may not realize this, but “America First” makes many people deeply uncomfortable. In 1941, as members of the America First movement campaigned against U.S. involvement in World War II and expressed sympathy for the Nazis, plenty of people already knew that Jews were being persecuted in Hitler’s Germany. Even Charles Lindbergh, the famous aviator who led the America First movement, knew it.

“It is not difficult to understand why Jewish people desire the overthrow of Nazi Germany,” Lindbergh said in Des Moines, Iowa, in September 1941. “The persecution they suffered in Germany would be sufficient to make bitter enemies of any race.”

But Lindbergh blamed Jewish Americans for pushing the country towards war, and warned that tolerance of Jews in America could not “survive” war with Germany. The greatest danger to the U.S., he argued, came not from the Axis powers but in what he saw as Jewish “ownership and influence in our motion pictures, our press, our radio and our government.”

This is dark stuff ― so dark it’s even inspired literature. Philip Roth, perhaps the most famous Jewish American writer, published The Plot Against America in 2004. The novel imagines an alternate U.S. history in which America First’s Lindbergh won the presidential election in 1940, defeating Franklin Delano Roosevelt. Things don’t go too well for the Jews after that.

“How can people like these be in charge of our country? If I didn’t see it with my own eyes, I’d think I was having a hallucination,” Roth’s father says in the book.

In real life, Lindbergh ― a celebrity who was at least as famous as Trump at a time when public anti-Semitism was far more acceptable than it is today ― actually faced some backlash for his speech, as The New Yorker’s Louisa Thomas noted in July:

Anti-Semitism was prevalent in Lindberg’s time; his attitudes were not fringe. He had not made a secret of his interest in eugenics, nor his racial attitudes, which today seem reprehensible. But with that 1941 speech he seemed to cross a line. He was strongly and swiftly condemned for his anti-Semitic and divisive words—not only by interventionists who were opposed to America First but by those who had lionized him. The Des Moines Register called his speech “so intemperate, so unfair, so dangerous in its implications that it cannot but turn many spadefuls in the digging of the grave of his influence in this country.” The Hearst papers, which were generally sympathetic to the non-interventionists—and open about their hatred of Franklin Roosevelt—condemned Lindbergh, calling his speech “un-American.” His home town took his name off its water tower.

Trump has received some similar criticism: “For many Americans, the term ‘America First’ will always be associated with and tainted by this history,” ADL CEO Jonathan Greenblatt warned last April. “In a political season that already has prompted a national conversation about civility and tolerance, choosing a call to action historically associated with incivility and intolerance seems ill-advised.”

The new president doesn’t seem chastened.

“To me, America First is a brand-new modern term,” he told The New York Times’ David Sanger in July. “I never related it to the past.”

But the past has a way of catching up to you. David Duke, the Holocaust denier and former KKK leader who endorsed Trump and celebrated his ascension to power, has long been happy with the slogan (he used it in his campaign for U.S. Senate), and can hear the dog whistle loud and clear.

Great Trump Speech, America First! Stop Wars! Defeat the Corrupt elites! Protect our Borders!, Fair Trade! Couldn't have said it better! — David Duke (@DrDavidDuke) July 22, 2016

After Trump’s speech on Friday, Duke tweeted:

https://t.co/IFcGFodAlm Dr. David Duke "Trump Inauguration Speech Declares War on the Neocons & Promotes Our Slogan "America First!" — David Duke (@DrDavidDuke) January 20, 2017

This story has been updated with an additional tweet from David Duke.

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