WASHINGTON ― In 2009, the historian David Kaiser, then a professor at the Naval War College in Newport, Rhode Island, got a call from a guy named Steve Bannon.

Bannon wanted to interview Kaiser for a documentary he was making based on the work of the generational theorists William Strauss and Neil Howe. Kaiser, an expert on Strauss and Howe, didn’t know Bannon from Adam, but he agreed to participate. He went to the Washington headquarters of the conservative activist group Citizens United, where Bannon was then based, for a chat.

Kaiser was impressed by how much Bannon knew about Strauss and Howe, who argued that American history operates in four-stage cycles that move from major crisis to awakening to major crisis. These crises are called “Fourth Turnings” — and Bannon believed the U.S. had entered one on Sept. 18, 2008, when Hank Paulson and Ben Bernanke went to Capitol Hill to ask for a bailout of the international banking system.

Illustration: Chris McGonigal: Getty

“He knew the theory,” Kaiser said. “He obviously enjoyed interviewing me.”

Bannon pressed Kaiser on one point during the interview. “He was talking about the wars of the Fourth Turnings,” Kaiser recalled. “You have the American Revolution, you have the Civil War, you have World War II; they’re getting bigger and bigger. Clearly, he was anticipating that in this Fourth Turning there would be one at least as big. And he really made an effort, I remember, to get me to say that on the air.”

Kaiser didn’t believe global war was preordained, so he demurred. The line of questioning didn’t make it into the documentary — a polemical piece, released in 2010, called “Generation Zero.”

Bannon, who’s now ensconced in the West Wing as President Donald Trump’s closest adviser, has been portrayed as Trump’s main ideas guy. But in interviews, speeches and writing — and especially in his embrace of Strauss and Howe — he has made clear that he is, first and foremost, an apocalypticist.

In Bannon’s view, we are in the midst of an existential war, and everything is a part of that conflict. Treaties must be torn up, enemies named, culture changed. Global conflagration, should it occur, would only prove the theory correct. For Bannon, the Fourth Turning has arrived. The Grey Champion, a messianic strongman figure, may have already emerged. The apocalypse is now.

“What we are witnessing,” Bannon told The Washington Post last month, “is the birth of a new political order.”

Drew Angerer via Getty Images President Donald Trump speaks on the phone with Australian Prime Minister Malcolm Turnbull on Jan. 28, 2017, with national security adviser Mike Flynn, center, and Chief Strategist Steve Bannon, at right.

Strauss died in 2007, and Howe did not respond to requests for comment. But their books speak for themselves. The first, Generations, released in 1991, set forth the idea that history unfolds in repetitive, predictable four-part cycles ― and that the U.S. was, and still is, going through the most recent cycle’s tail end. (In Generations, Strauss and Howe became perhaps the first writers to use the term “millennials” to describe the current cohort of young people.)

Strauss and Howe’s theory is based on a series of generational archetypes — the Artists, the Prophets, the Nomads and the Heroes — that sound like they were pulled from a dystopian young adult fiction series. Each complete four-part cycle, or saeculum, takes about 80 to 100 years, in Strauss and Howe’s reckoning. The Fourth Turning, which the authors published in 1997, focuses on the final, apocalyptic part of the cycle.

Strauss and Howe postulate that during this Fourth Turning crisis, an unexpected leader will emerge from an older generation to lead the nation, and what they call the “Hero” generation (in this case, millennials), to a new order. This person is known as the Grey Champion. An election or another event — perhaps a war — will bring this person to power, and their regime will rule throughout the crisis.

“The winners will now have the power to pursue the more potent, less incrementalist agenda about which they had long dreamed and against which their adversaries had darkly warned,” Strauss and Howe wrote in The Fourth Turning. “This new regime will enthrone itself for the duration of the Crisis. Regardless of its ideology, that new leadership will assert public authority and demand private sacrifice. Where leaders had once been inclined to alleviate societal pressures, they will now aggravate them to command the nation’s attention.”

Cyclical models of history are something academics kick around every now and then, said Sean Wilentz, an American history professor at Princeton University. But the idea has not caught on among historians or political actors.

“It’s just a conceit. It’s a fiction, it’s all made up,” Wilentz said about cyclical historical models. “There’s nothing to them. They’re just inventions.”

Michael Lind, a historian and co-founder of the New America Foundation, a liberal think tank, has called Strauss and Howe’s work “pseudoscience” and said their “predictions about the American future turn out to be as vague as those of fortune cookies.”

But Bannon bought it.

“This is the fourth great crisis in American history,” Bannon told an audience at the Liberty Restoration Foundation, a conservative nonprofit, in 2011. “We had the Revolution. We had the Civil War. We had the Great Depression and World War II. This is the great Fourth Turning in American history, and we’re going to be one thing on the other side.”

Major crises “happen in about 80- or 100-year cycles,” Bannon told a conference put on by the Republican women’s group Project GoPink that same year. “And somewhere over the next 10 or 20 years, we’re going to come through this crisis, and we’re either going to be the country that was bequeathed to us or it’s going to be something that’s completely or totally different.”

The “Judeo-Christian West is collapsing,” he went on. “It’s imploding. And it’s imploding on our watch. And the blowback of that is going to be tremendous.”

War is coming, Bannon has warned. In fact, it’s already here.

It’s war. It’s war. Every day, we put up: America’s at war, America’s at war. We’re at war. White House Chief Strategist Steve Bannon, 2015

“You have an expansionist Islam and you have an expansionist China,” he said during a 2016 radio appearance. “They are motivated. They’re arrogant. They’re on the march. And they think the Judeo-Christian West is on the retreat.”

“Against radical Islam, we’re in a 100-year war,” he told Political Vindication Radio in 2011.

“We’re going to war in the South China Seas in the next five to 10 years, aren’t we?” Bannon asked during a 2016 interview with Reagan biographer Lee Edwards.

“We are in an outright war against jihadist Islamic fascism,” he said in a speech to a Vatican conference in 2014. “And this war is, I think, metastasizing far quicker than governments can handle it.”

In a 2015 radio appearance, Bannon described how he ran Breitbart, the far-right news site he chaired at the time. “It’s war,” he said. “It’s war. Every day, we put up: America’s at war, America’s at war. We’re at war.”

To confront this threat, Bannon argued, the Judeo-Christian West must fight back, lest it lose as it did when Constantinople fell to the Ottomans in 1453. He called Islam a “religion of submission” in 2016 — a refutation of President George W. Bush’s post-9/11 description of Islam as a religion of peace. In 2007, Bannon wrote a draft movie treatment for a documentary depicting a “fifth column” of Muslim community groups, the media, Jewish organizations and government agencies working to overthrow the government and impose Islamic law.

Carlos Barria / Reuters Trump signs an executive order he said would impose tighter vetting to prevent foreign terrorists from entering the United States, Jan. 27, 2017.

“There’s clearly a fifth column here in the United States,” Bannon warned in July 2016. “There’s rot at the center of the Judeo-Christian West,” he said in November 2015. “Secularism has sapped the strength of the Judeo-Christian West to defend its ideals,” he argued at the Vatican conference. The “aristocratic Washington class” and the media, he has claimed, are in league with the entire religion of Islam and an expansionist China to undermine Judeo-Christian America.

This sort of existential conflict is central to Strauss and Howe’s predictions. There are four ways a Fourth Turning can end, they argued, and three of them involve some kind of massive collapse. America might “be reborn,” and we’d wait another 80 to 100 years for a new cycle to culminate in a crisis again. The modern world — the era of Western history that Strauss and Howe believe began in the 15th century — might come to an end. We might “spare modernity but mark the end of our nation.” Or we might face “the end of man,” in a global war leading to “omnicidal Armageddon.”

Now, a believer in these vague and unfounded predictions sits in the White House, at the right hand of the president.

“We’re gonna have to have some dark days before we get to the blue sky of morning again in America,” Bannon warned in 2010. “We are going to have to take some massive pain. Anybody who thinks we don’t have to take pain is, I believe, fooling you.”

“This movement,” he said in November, “is in the top of the first inning.”

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