Donald Trump's former chief strategist has vowed to go to war against the president's opponents, after being fired from his job at the White House.
Steve Bannon, who has returned as head of ultra-conservative website Breitbart News, said he would fight for the agenda that won Mr Trump the election.
"I've got my hands back on my weapons," he said. "It's Bannon the Barbarian."
Mr Bannon helped shape the America First campaign message but fell foul of more moderate White House forces.
The 63-year-old has been accused of voicing anti-Semitic and white supremacist views.
He is the latest high-profile figure to leave the White House team. National Security Adviser Michael Flynn; press secretary Sean Spicer; chief of staff Reince Priebus and communications director Anthony Scaramucci have all gone.
Mr Trump paid tribute to Mr Bannon in an early-morning tweet on Saturday.
I want to thank Steve Bannon for his service. He came to the campaign during my run against Crooked Hillary Clinton - it was great! Thanks S
End of Twitter post by @realDonaldTrump
There had been suggestions Mr Trump was under renewed pressure to sack Mr Bannon following the violence at a far-right rally in Charlottesville, Virginia, last weekend, when a car was driven into counter-protesters, killing a woman.
But he told the Weekly Standard that he had informed Chief of Staff John Kelly and Mr Trump on 7 August that he would announce his resignation on the 14th. The tumult over the violence in Charlottesville postponed the announcement, he said.
President Trump had hinted at the situation during his controversial press briefing on the Virginia violence on Tuesday.
Media captionSome of the people who have resigned or been fired under President Trump
Although the president had defended Mr Bannon as "not a racist", saying he had received an unfair press, Mr Trump said "we'll see what happens" about him.
The only statement about Mr Bannon's sacking on Friday came from Trump spokeswoman Sarah Huckabee Sanders, who said: "We are grateful for his service and wish him the best."
In his Weekly Standard interview, Mr Bannon said: "The Trump presidency that we fought for, and won, is over.
"We still have a huge movement, and we will make something of this Trump presidency. But that presidency is over. It'll be something else. And there'll be all kinds of fights, and there'll be good days and bad days, but that presidency is over."
He added: "In many ways I think I can be more effective fighting from the outside for the agenda President Trump ran on. And anyone who stands in our way, we will go to war with."
End of Twitter post by @joelpollak
Mr Bannon added: "I built a [expletive] machine at Breitbart. And now I'm about to go back, knowing what I know, and we're about to rev that machine up."
Breitbart itself carried the headline: 'Populist Hero' Stephen K Bannon Returns Home to Breitbart.
News editor-in-chief Alex Marlow said: "Breitbart gained an executive chairman with his finger on the pulse of the Trump agenda."
Breitbart executive Joel Pollak responded to the return of Mr Bannon with a singled-worded, hashtag tweet: #WAR.
Taking credit did him in
By Anthony Zurcher, BBC North America reporter
Steve Bannon may be out as a senior White House adviser, but Bannonism - if that's what it can properly be called - is still firmly entrenched in the White House.
Donald Trump has repeatedly boasted that the success of his presidential campaign should properly be attributed to him, not Mr Bannon. And, in the end, Mr Bannon's desire to take credit for that win may have been what did him in.
It certainly wasn't because of any sharp ideological divides between the president and the former head of Breitbart News.
Border security, aggressive trade protectionism, immigration reform and a certain kind of cultural nostalgia - all were themes that Mr Trump ran on from the start, which Mr Bannon only sharpened and focused. They're also issues Mr Trump has pushed in recent weeks, even as Mr Bannon has been increasingly marginalised.
Mr Bannon's firing will be seen as a win for chief of staff John Kelly, whose attempts to instil discipline in the White House will get a boost without the free-wheeling Mr Bannon roaming the hallways.
Trump was Trump before Mr Bannon came on the scene, however. And as the rollercoaster ride that was politics this week indicates, the president isn't changing anytime soon.
Mr Trump raised eyebrows this year when he elevated Mr Bannon to the National Security Council, the main group advising the president on national security and foreign affairs.
But he was subsequently removed in a move that was seen as a sign of National Security Adviser HR McMaster's growing influence over the president.
Mr Bannon has reportedly feuded with Mr McMaster as well as Gary Cohn, the director of the president's National Economic Council and a former Goldman Sachs chief viewed as a "globalist".
Mr Cohn, along with President Trump's son-in-law Jared Kushner and daughter, Ivanka Trump, were viewed as threats to Mr Bannon's White House agenda.
Mr Trump had reportedly grown weary of Mr Bannon taking credit for his victory and also saw him as a serial leaker of information to the press.
Mr Bannon's interview this week with the American Prospect, a liberal magazine, also reportedly infuriated the president.
The White House aide was quoted as dismissing the idea of a military solution in North Korea, undercutting Mr Trump