The Post's Dan Balz says the firing of chief strategist Stephen K. Bannon simultaneously changes everything and nothing for the Trump administration. (Bastien Inzaurralde,Jhaan Elker/The Washington Post)

The end of Stephen K. Bannon’s stormy White House tenure frees the investment banker turned populist messenger to expand his reach as a potent force in the media landscape, giving him an elevated platform for the nationalist movement he has long championed.

Bannon will do so in conjunction with the wealthy Mercer family, conservative mega-donors who served as his patrons in an array of enterprises before he joined the Trump campaign.

The former chief strategist for President Trump is returning as executive chairman of Mercer-backed Breitbart News, the pugilistic conservative website he helped guide before joining Trump’s campaign last August, Breitbart announced.

Hours after his departure was confirmed Friday by the White House, Bannon was back in charge at the website, chairing the evening editorial meeting.

“The populist-nationalist move­ment got a lot stronger today,” Breitbart News Editor-in-Chief Alex Marlow said in release with the headline “ ‘Populist Hero’ Stephen K. Bannon Returns Home to Breitbart.”

Associates said Bannon may also partner on a new venture with the Mercers — potentially another news organization.

Bannon declined to comment. But in an interview with the Weekly Standard, Bannon said he feels “jacked up.”

“Now I’m free,” he said. “I’ve got my hands back on my weapons. Someone said, ‘It’s Bannon the Barbarian.’ I am definitely going to crush the opposition.”

A rapid return to the media puts the former Hollywood producer and news executive back on familiar ground, allowing him to unspool his views about the threats of globalization and radical Islam, unconstrained by politics or protocol. “Now he is unencumbered to go do what he thinks,” said Scot Vorse, a friend of 35 years and former business colleague.

“I am pretty confident that Steve’s job and goal will not change: to make President Trump’s campaign mission come true,” he added. “We will see whether Steve is more helpful inside or outside.”

Bannon is exiting the White House a much more prominent figure than a year ago — heralded on the right as a leading anti-elite insurgent and pilloried by critics as a purveyor of an “America First” philosophy that has energized white supremacists.

“Look, he’s a force to be reckoned with,” said Pat Caddell, a veteran Democratic pollster who has worked with Bannon. “He’s willing to engage in the political combat, and so I expect he’ll be doing that. His sense of history and the moment are very powerful. He will be in the fight, for sure.”

Robert Kuttner, co-editor of the American Prospect, got an unexpected interview with White House chief strategist Stephen K. Bannon on Aug. 15. (Peter Stevenson/The Washington Post)

Before he burst onto the national stage, Bannon sought to shape the country’s political landscape through a series of provocative media projects, some of them ­financed by the Mercers, who he met through the late conservative entrepreneur Andrew Breitbart.

Bannon directed and produced documentaries such as “Generation Zero,” an examination of the global economic crisis, and “Battle for America,” which hammered an “arrogant, and ever-expanding central government.” His film “Clinton Cash,” financed by the Mercers, argued that Democratic presidential nominee Hillary Clinton was a captive of wealthy interests. And under his leadership, Breitbart News emerged as the voice of the disaffected right.

“I think he really wants to change the world,” said Julia Jones, who was Bannon’s screenwriting partner for 16 years.

Jones said she could envision Bannon setting up his own cable news network, one that he would position to challenge Fox News, which she said he complained to her was too liberal.

“It would give him a much larger platform than Breitbart,” she said.

Whether Bannon will use his megaphone to promote the Trump administration or to slam it remains to be seen. Inside the embattled White House, the chief strategist frequently tangled with Trump’s son-in-law, Jared Kushner, and other presidential advisers over trade and foreign policy. His primary allegiance, friends said, is to the people who put Trump into office.

“He views his role as the protector of the movement of the ­working-class coalition that elected Trump,” said a person close to him, who requested anonymity to describe private conversations.

Bannon is not angry with Trump personally, the person added, but is “certainly disappointed in the way the White House is going. There’s a sense it’s drifting toward the moderate, mushy middle.”

Caddell said he does not expect Bannon to critique Trump personally. “There is a fundamental loyalty there,” he said. He said Bannon’s focus will be on the establishment forces that he believes are leading the president astray.

Indeed, Bannon told Bloomberg News on Friday that he is “going to war for Trump against his opponents — on Capitol Hill, in the media, and in corporate America.”

Still, there are signs that some Bannon allies are gearing up for battle. On Friday, Breitbart jabbed at the White House over Bannon’s departure, with senior editor-at-large Joel B. Pollak tweeting “#WAR.” He warned that losing the White House chief strategist “may turn out to be the beginning of the end for the Trump administration, the moment Donald Trump became Arnold Schwarz­enegger,” referring to the former California governor and movie star who irked many conservatives.

Neither Pollak nor other senior Breitbart executives responded to requests for comment.

Beyond Breitbart, Bannon’s next moves are also expected to involve hedge fund executive Robert Mercer and his daughter Rebekah, who collaborated with Bannon on at least five ventures before he joined the Trump campaign. Along with his role at Breitbart, Bannon served as vice president and secretary of the Mercer-funded Cambridge Analytica, a data science company that worked for Trump’s campaign.

He and Robert Mercer huddled earlier this week to discuss plans, according to someone familiar with the meeting.

“They have a very strong working relationship together, and I would be shocked if we don’t hear of a major initiative involving Steve and the Mercers in the next 30 and 60 days,” said a person familiar with the family’s views, who requested anonymity to describe the thinking of the famously private donors. “They don’t walk in lockstep in terms of their views, but they like the fact that Steve gets results, and they think money put into ventures he’s involved in is money well spent.”

Bannon earned at least $917,000 in 2016, drawing at least $545,000 of that from four Mercer-backed ventures, according to a personal financial disclosure he filed in late March.

At the time, he estimated that his assets were worth between $11.8 million and $53.8 million. Among his holdings: three rental properties and a strategic consulting firm he said was worth between $5 million and $25 million. The filing also showed that Bannon had significant cash reserves, reporting at least $1.1 million in three different U.S. bank accounts.

Robert Costa and David Weigel contributed to this report.