WASHINGTON ― A senior national security official in the Trump administration wrote under a pseudonym last year that Islam is an inherently violent religion that is “incompatible with the modern West,” defended the World War II-era America First Committee, which included anti-Semites, as “unfairly maligned,” and called diversity “a source of weakness, tension and disunion.”

Michael Anton, who served as a speechwriter for President George W. Bush, joined President Donald Trump’s administration earlier this year as a staffer on the National Security Council. But in the year leading up to the 2016 election, Anton operated as an anonymous booster of then-candidate Trump. Using the pen name Publius Decius Mus (the name of a self-sacrificing Roman consul), Anton promoted Trump’s anti-Islam, anti-immigration platform on fringe websites. The Weekly Standard revealed Publius to be Anton last week.

As Publius, Anton is best-known for his September 2016 article, “The Flight 93 Election,” which argued that, like the passengers on the aircraft hijacked by al Qaeda on Sept. 11, 2001, Americans in 2016 needed to “charge the cockpit” and prevent Hillary Clinton from winning the election — or die. The article, which ran in the Claremont Review of Books, was circulated widely on conservative and white nationalist websites. The New Yorker declared it “the most cogent argument for electing Trump” but cited the responses by Ross Douthat of The New York Times that he’d “rather risk defeat at my enemies’ hands than turn my own cause over to a incompetent tyrant” and by Jonah Goldberg of National Review that its central metaphor is “grotesquely irresponsible.”

“The Flight 93 Election” wasn’t Anton’s only — or most provocative — defense of his future boss. In March, six months before the Flight 93 piece began circulating, Anton published a longer and lesser-noticed essay, “Toward a Sensible, Coherent Trumpism,” in the Unz Review, a website that hosts both far-right and far-left commentary. Journal of American Greatness, a blog that closed last year, republished the 6,000-word piece, and Breitbart, a news site known for promoting white supremacist and anti-Semitic views, which openly supported Trump’s election, ran an excerpt. (American Bridge, a Democratic opposition research group, noted the Journal of American Greatness version of the essay in an email to The Huffington Post.)

Jabin Botsford/The Washington Post via Getty Images National Security Council staffer Michael Anton at a recent White House briefing.

According to an editor’s note on the Journal’s website, a “(semi-)prominent conservative think-tank” — presumably the Claremont Institute—rejected the piece because its arguments against immigration were grounded in emotion rather than logic. (The institute’s Claremont Review of Books did not immediately respond to a request for comment.)

Anton devoted 1,000 words of the March essay to defending Trump’s “America first” slogan, which is eerily reminiscent of the America First Committee, a group that urged the U.S. to stay out of World War II, sometimes by invoking anti-Semitic stereotypes. When American Jews urged the U.S. to intervene on behalf of Jews facing genocide in Nazi Germany, AFC spokesman (and famed aviator) Charles Lindbergh accused them of “agitating for war.” Jewish Americans’ “great danger to this country lies in their large ownership and influence in our motion pictures, our press, our radio, and our government,” Lindbergh said in 1941.

Bettmann/Getty Images Aviator and America First Committee spokesman Charles Lindbergh, left, warned in 1941 that Jewish Americans threatened the country because of their influence in films, the media, radio and government.

Lindbergh’s comments were shocking, even at a time when outright anti-Semitism was more publicly acceptable. “The voice is the voice of Lindbergh, but the words are the words of Hitler,” The San Francisco Chronicle wrote in an editorial.

But the America First Committee, according to Anton, was “unfairly maligned” and the whole episode represents only “an alleged stain on America’s past.”

The White House did not respond to a request for comment. Anton did not respond to a request for comment before publication. He addressed this article four days later in an interview with the editors of the website American Greatness, where he is a former contributing editor. The website appears to be run by the same team as the now-defunct Journal of American Greatness blog.

The America First Committee was “primarily an isolationist movement, but there were anti-semitic elements that supported it,” he told American Greatness in the interview published Sunday. “What the Left has tried to do ― with much success, unfortunately ― is retcon the committee as primarily an anti-Jewish group when that’s not what it was,” he continued.

Throughout the essay published last year, Anton argues that immigration inevitably hurts the U.S. Here’s one passage:

[One] source of Trump’s appeal is his willingness — eagerness — gleefulness! — to mock the ridiculous lies we’ve been incessantly force-fed for the past 15 years (at least) and tell the truth. “Diversity” is not “our strength”; it’s a source of weakness, tension and disunion. America is not a “nation of immigrants”; we are originally a nation of settlers, who later chose to admit immigrants, and later still not to, and who may justly open or close our doors solely at our own discretion, without deference to forced pieties. Immigration today is not “good for the economy”; it undercuts American wages, costs Americans jobs, and reduces Americans’ standard of living. Islam is not a “religion of peace”; it’s a militant faith that exalts conversion by the sword and inspires thousands to acts of terror — and millions more to support and sympathize with terror.

Anton acknowledged in the March essay that Trump may have gone too far proposing a ban on all Muslims from entering the U.S. — surely business travelers from Dubai should be allowed in, he argued. But he praised Trump for his broader effort to limit the number of Muslims who are allowed to live in America. It is obvious, he wrote, that “Islam and the modern West are incompatible…. Only an insane society, or one desperate to prove its fidelity to some chimerical ‘virtue,’ would have increased Muslim immigration after the September 11th attacks. Yet that is exactly what the United States did. Trump has, for the first time, finally forced the questions: Why? And can we stop now?”

Pew estimated last year that about 1 percent of the U.S. population is Muslim.

AFP/Getty Images President Donald Trump's executive order targeting citizens of Muslim-majority countries was met with nationwide protests, including this one at Los Angeles International Airport.

Anton wrote that he accepts that “not all Muslims are terrorists, blah, blah, blah, etc.” But even so, he asked, “what good has Muslim immigration done for the United States and the American people?”

Over the past 20 years, immigration has had a positive effect on long-term economic growth in the U.S. and minimal effect on the wages and employment levels of individuals born in the U.S., a panel of prominent economists concluded last year.

In the American Greatness interview published on Sunday, Anton said that America has previously benefited from immigration, but that time has passed. “My view is that we long ago passed the point of diminishing returns and high immigration is no longer a net benefit to the existing American citizenry,” he said.

Anton’s heterodoxies aren’t limited to issues of immigration. It’s not America’s job to “democratize the world,” he argued in the March essay. “The Iraq War was a strategic and tactical blunder that destroyed a country (however badly governed), destabilized a region, and harmed American interests.” But like Trump, who initially supported the invasion of Iraq but has repeatedly claimed otherwise, Anton’s position on the war seems to have shifted over the years: According to The Weekly Standard, he was part of the team within the Bush administration that pushed for the invasion. (After this article was published, Anton told American Greatness that he supported the invasion of Iraq, but now believes it was a mistake. He added that he believes the subsequent troop surge was the right thing to do and that the U.S. withdrew too soon.)

“As the experience of Europe has decisively shown, we in the West don’t have the power to change Muslims,” he wrote last March. “The reverse is true: when we welcome them en masse into our countries, they change us — and not for the better.”

Anton’s apocalyptic warnings about Islam, immigrants and diversity echo the ideology of Steve Bannon, who ran Breitbart News before becoming Trump’s chief strategist. Although Trump has also staffed his White House with establishment Republicans, including two former Republican National Committee leaders in Chief of Staff Reince Priebus and Press Secretary Sean Spicer — it is Bannon’s worldview that appears to guide high-level policy decisions.

Bannon reportedly played a key role in creating Trump’s travel ban. When the Department of Homeland Security concluded that the ban shouldn’t apply to legal permanent U.S. residents, Bannon pushed back, CNN reported. (Days later, the White House announced that green card holders were exempted from the travel ban.)

The Journal of American Greatness, the blog that republished Anton’s essay, was taken down in mid-2016, but its posts are still viewable using a digital archive tool.

“The inspiration for this journal was a profound discomfort with the mode of thought that has come to dominate political discourse — an ideological mode that makes nonsense of the reality of American life,” the journal’s editors wrote in a farewell note to readers. “The unanticipated recognition that we have received, however, also makes clear that many others similarly felt the desirability of breaking out of conservatism’s self-imposed intellectual stagnation.”

The blog had started as “an inside joke,” they noted. But at some point, they wrote, it “ceased to be a joke.”

This story has been updated to include Anton’s post-publication comments in an interview with the website American Greatness.