In November 2015, Stephen K. Bannon — then the executive chairman of Breitbart News — was hosting a satellite radio show. His guest was Montana Representative Ryan Zinke, who opposed President Obama’s plan to resettle some Syrian refugees in the United States.

“We need to put a stop on refugees until we can vet,” Mr Zinke said.

Mr Bannon cut him off.

“Why even let ’em in?” he asked.

Mr Bannon said that vetting refugees from Muslim-majority countries would cost money and time. “Can’t that money be used in the United States?” he said. “Should we just take a pause and a hiatus for a number of years on any influx from that area of the world?”

In the years before Mr Bannon grabbed the world’s attention as President Trump’s chief White House strategist, he was developing and articulating a fiery populist vision for remaking the United States and its role in the world.

Mr Bannon’s past statements, aired primarily on Breitbart and other conservative platforms, serve as a road map for the controversial agenda that has roiled Washington and shaken the global order during Mr Trump’s first two weeks in office.

Now, at the centre of power in the White House, Mr Bannon is moving quickly to turn his ideas into policy, helping direct the biggest decisions of Mr Trump’s administration. The withdrawal from a major trade pact. A ban on all visitors from seven majority-Muslim countries. And — in an echo of that conversation with Mr Zinke, who is now Mr Trump’s nominee for interior secretary — there was a temporary ban on all new refugees.

The result has been intense fury from Democrats, discomfort among many Republicans, and a growing sense of unease in the world that Mr Trump intends to undermine an America-centered world that has lasted 70 years. This sense of turmoil, welcomed by many Trump supporters as proof that the new president is following through on his vow to jolt Washington, reflects the sort of transformation that Mr Bannon has long called for.

That worldview, which Mr Bannon laid out in interviews and speeches over the past several years, hinges largely on Mr Bannon’s belief in American “sovereignty.” Mr Bannon said that countries should protect their citizens and their essence by reducing immigration, legal and illegal, and pulling back from multinational agreements.

As nationwide protests against President Trump’s immigration mandate rage on, he reshuffled the National Security Council and put chief strategist and former Breitbart News chair Stephen Bannon in an unprecedented national security role (Washington Post)

At the same time, Mr Bannon was concerned that the United States and the “Judeo-Christian West” were in a war against an expansionist Islamic ideology — but that they were losing the war by not recognising what it was. Mr Bannon said this fight was so important, it was worth overlooking differences and rivalries with countries like Russia.

It is not yet clear how far Mr Bannon will be able to go to enact his agenda. His early policy moves have been marred by administrative chaos. But his world view calls for bigger changes than those already made.

In the past, Mr Bannon had wondered aloud whether the country was ready to follow his lead. Now, he will find out.

“Is that grit still there, that tenacity, that we’ve seen on the battlefields... fighting for something greater than themselves?” Mr Bannon said in another radio interview last May, before he joined the Trump campaign.

That, said Mr Bannon, is “one of the biggest open questions in this country”.

Mr Bannon, 62, is a former Navy officer and Goldman Sachs banker who made a fortune after he acquired a share of the royalties from a fledgling TV show called “Seinfeld.” In the past 15 years, he shifted into entertainment and conservative media, making films about Ronald Reagan and Sarah Palin and then taking a lead role at Breitbart News.

At Breitbart, Mr Bannon cemented his role as a champion of the alt-right, the anti-globalism movement that has attracted support from white supremacists and found a home on the far-right website.

Mr Bannon also forged a rapport with Mr Trump, interviewing the businessman-candidate on his show and then, in August 2016, joining the campaign as chief executive.

Now, Mr Bannon has become one of the most powerful men in America. And he is not afraid to say so.

In interviews with reporters since Mr Trump’s election, Mr Bannon has eschewed the traditional it-is-all-about-the-boss humility of presidential staffers.

“Dick Cheney. Darth Vader. Satan. That’s power,” he told the Hollywood Reporter in November, embracing the comparisons of him to those figures.

Donald Trump's closest advisor Steve Bannon thinks there will be war with China in the next few years

In the same interview, Mr Bannon compared himself to a powerful aide to England’s Henry VIII — an aide who helped engineer a world-shaking move of his era, the split of the Church of England from the Catholic Church.

“I am Thomas Cromwell in the court of the Tudors,” Mr Bannon told the Hollywood Reporter.

To explore Mr Bannon’s world view, The Washington Post reviewed hours of radio interviews that Mr Bannon conducted while hosting a Breitbart radio talk show, as well as speeches and interviews he has given since 2014.

Mr Bannon did not respond to a request for comment made on Tuesday afternoon.

In his public statements, Mr Bannon espoused a basic idea that Mr Trump would later seize as the centrepiece of his campaign.

While others saw the world rebounding from the financial crisis of 2008, Mr Bannon just saw it becoming more divided by class.

The elites that had caused the crisis — or, at least, failed to stop it — were now rising higher. Everyone else was being left behind.

“The middle class, the working men and women in the world... are just tired of being dictated to by what we call the party of Davos,” Mr Bannon said in a 2014 speech to a conference at the Vatican in a recording obtained by BuzzFeed. Davos is a Swiss ski resort that hosts an annual conclave of wealthy and powerful people.

Mr Bannon blamed both major political parties for this system and set out to force his ideas on an unwilling Republican leadership.

What he wanted, he said again and again, was “sovereignty.” Both in the United States and in its traditional allies in Western Europe.

Steve Bannon calls liberal women 'a bunch of dykes'

On one of the first Breitbart Radio shows, in early November 2015, Mr Bannon praised the growing movement in Britain to exit the European Union. He said that the British had joined the EU merely as a trading federation but that it had grown into a force that had stripped Britons of sovereignty “in every aspect important to their own life”.

Mr Bannon has been supportive of similar movements in other European countries to pull out of the union. Mr Trump has echoed those sentiments in his first few days as president. It is a remarkable shift in US policy: After decades of building multinational alliances as a guarantee of peace, now the White House has indicated it may undermine them.

Mr Bannon, in his 2014 speech at the Vatican, cast this as a return to a better past.

“I think strong countries and strong nationalist movements in countries make strong neighbours,” Mr Bannon said. “And that is really the building blocks that built Western Europe and the United States, and I think it’s what can see us forward.”

In the case of the United States, Mr Bannon was sceptical of multinational trade pacts, saying that they ceded control. In a radio interview in November 2015, Alabama Senator Jeff Sessions agreed with Mr Bannon.

“We shouldn’t be tying ourselves down like Gulliver in the land of Lilliputians with so many strings a guy can’t move,” said Mr Sessions, who is now Mr Trump’s nominee to become attorney general. He was referring to a scene from the novel “Gulliver’s Travels” in which the hero is tied down by a race of tiny men. “That is where we are heading, and it’s not necessary.”

One solution put forward by Mr Bannon: the United States should pursue bilateral trade agreements — one country at a time — rather than multi-country agreements such as the Trans-Pacific Partnership supported by Obama.

He suggested as much to Mr Trump himself, when the candidate appeared on his show in November 2015.

“Trump brings [a deal] back to the Senate and gets his bilateral trade deal with Taiwan or with Japan approved by two-thirds of the Senate,” Mr Bannon said. “And you have to go argue, ‘Hey, this is why it’s a good deal.’ And that’s the way the Founders wanted it.”

On a March 2016 episode, Mr Bannon said that restoring sovereignty meant reducing immigration. In his radio shows, he criticised the federal H-1B visa programmes that permit US companies to fill technical positions with workers from overseas.

Sean Spicer defends Steve Bannon sitting in on national security council meetings

The “progressive plutocrats in Silicon Valley,” Mr Bannon said, want unlimited ability to go around the world and bring people back to the United States. “Engineering schools,” Mr Bannon said, “are all full of people from South Asia, and East Asia... They’ve come in here to take these jobs.” Meanwhile, Mr Bannon said, American students “can’t get engineering degrees; they can’t get into these graduate schools because they are all foreign students. When they come out, they can’t get a job.”

“Don’t we have a problem with legal immigration?” asked Mr Bannon repeatedly.

“Twenty percent of this country is immigrants. Is that not the beating heart of this problem?” he said, meaning the problem of native-born Americans being unable to find jobs and rising wages.

In another show, Mr Bannon had complained to Trump that so many Silicon Valley chief executives were South Asian or Asian. This was a rare time when Mr Trump — normally receptive to Mr Bannon’s ideas on-air — pushed back. “I still want people to come in,” Mr Trump said. “But I want them to go through the process.”

So far, Mr Trump has made no changes to the high-skilled visa program. This week, White House press secretary Sean Spicer said that the Trump administration may reexamine the program.

Even as Mr Bannon was calling for a general retreat from multinational alliances, however, he was warning of the need for a new alliance — involving only a subset of the world’s countries.

The “Judeo-Christian West” was at war, he said, but didn’t seem to understand it yet.

“There is a major war brewing, a war that’s already global,” Bannon said at the Vatican in 2014, at a time when the Islamic State was gaining territory. “Every day that we refuse to look at this as what it is — and the scale of it, and really the viciousness of it — will be a day where you will rue that we didn’t act.”

Mr Bannon has given few details about the mechanics of the war he thinks the West should fight. But he has been clear that it is urgent enough to take priority over other rivalries and worries.

In his talk at the Vatican, Mr Bannon was asked about Russian President Vladi­mir Putin. Mr Bannon’s answer was two-sided.

“I think that Putin and his cronies are really a kleptocracy, that are really an imperialist power that want to expand,” he said. But, Mr Bannon said, there were bigger concerns than Russia — and there was something to admire in Mr Putin’s call for more traditional values.

“However, I really believe that in this current environment, where you’re facing a potential new caliphate that is very aggressive that is really a situation — I’m not saying we can put [Russia] on a back burner — but I think we have to deal with first things first,” Mr Bannon said.

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If Mr Bannon succeeds, Mr Bannon’s own comparison, to England’s Thomas Cromwell, might be apt — to a point.

“The analogy — if it’s going to work — is that Bannon has his own agenda, which he will try to use Trump for, and will try to exploit the power that Trump has given him, without his master always noticing,” said Diarmaid MacCulloch, a professor of history at England’s Oxford University.

But Cromwell was later executed, after Henry VIII turned against him. For a man like that, Mr MacCulloch said, power is always tenuous: “It’s very much dependent on the favour of the king.”