White House Chief Strategist Stephen K. Bannon is leaving the White House.

In a statement, the White House said “White House Chief of Staff John Kelly and Steve Bannon have mutually agreed today would be Steve’s last day. We are grateful for his service and wish him the best.”

The details of exactly when and how this decision were made is not immediately clear. New York Times reporter Maggie Haberman said one source told her Bannon had resigned himself earlier this month, setting Aug. 14 — almost exactly one year from the date he joined Trump’s campaign — as his last day.

Before joining Trump’s campaign, Bannon was executive of Breitbart News, a far-right news and opinion site. It is often criticized for advancing racist, anti-Semitic and misogynistic views, catering to the so-called “alt-right” movement, which is a mix of white nationalism, neo-Nazi beliefs and extreme populism.

Late Friday, the Associated Press reported Bannon would return to the site, saying he led an editorial meeting that evening.

Why has Bannon been so controversial? Since the 2016 election, Bannon has been a key and controversial adviser in the White House. Many have seen him as a driving force behind the president’s travel ban and trade decisions, including his intentions to withdraw from the Paris Climate Accord.

Author Josh Green recently told the NewsHour that “one of the effects that Bannon had on politics was to open up a kind of sluice gate of people who existed really only on the fringes of American and far-right talk radio and on Internet boards and try and bring them into the political conversation, the mainstream political conversation, by giving them a voice on places like Breitbart News.”

Bannon, who once referred to Breitbart as “the platform for the alt-right,” described that same group as “losers” and “a collection of clowns” in a rare, lengthy interview with the liberal publication The American Prospect.

John Yang talked with Journalist Robert Kuttner of The American Prospect and Joshua Green, author of “Devil’s Bargain,” about Bannon’s impromptu interview.

Tensions escalated after Charlottesville: After the rally turned violent in Charlottesville, Bannon’s particular brand of right-wing politics was again called into question. In his interview with The American Prospect, he also made a rare public contradiction on the president’s strategy on North Korea and talked about purging his rivals in the Defense and State departments.

Four minority House caucus groups penned a letter calling for the removal of several White House aides, including Bannon. Conservative media mogul Rupert Murdoch, too, had reportedly pressed the president to fire Bannon.

“We’ll see what happens with Mr. Bannon,” the president told reporters Tuesday at a news conference at the Trump Tower in New York.

“I like Mr Bannon. He’s a friend of mine. But Mr. Bannon came on very late … I went through 17 senators, governors and I won all the primaries. Mr. Bannon came on very much later than that,” he added.

This is the latest in a string of White House departures: Bannon’s departure is the second major exit under new Chief of Staff John Kelly; White House Communications Director Anthony Scaramucci was removed from his position in late July. It also follows the departure of several other key members of Trump’s team at the White House, including former chief of staff Reince Priebus and former press secretary Sean Spicer.

Trump’s previous top strategists have also served short terms: PBS NewsHour’s Lisa Desjardins points out many of the president’s previous top advisers have also served short terms.

Corey Lewandowski served as campaign manager from June 16, 2015 to June 20, 2016

Paul Manafort took over the campaign from June 21 to Aug. 17, 2016

Bannon, whose position in the White House was at times opaque, served from Aug. 17, 2016 to Aug. 18, 2017.

But loyalty also goes a long way in the White House

Outside of his family:

Hope Hicks, Trump’s director of strategic communications, has worked with Trump since the beginning of his campaign — and with Ivanka Trump before that. She’s serving as interim White House Communications Director while press Secretary Sarah Huckabee Sanders searches for a permanent replacement for Anthony Scaramucci.

Kellyanne Conway, counsel to the president, was hired in July 2016. She’s served a number of roles in Trump’s campaign and White House.

Omarosa Manigault, once a contestant on the first season of “The Apprentice,” was also hired in July 2016. She’s the director of communications for the Office of Public Liaison for Trump.

There are also a handful of lower-level staff — like Dan Scavino, the White House Director of Social Media and an assistant to the president — who have worked for Trump for a number of years.

Will this change Trump’s positions or policies?

Bannon’s departure is a triumph for corporate conservatives, Kelly, and possibly China, says E.J. Dionne, an opinion writer at the Washington Post and senior fellow at the Brookings Institution. “Bannon was the China hawk on trade,” Dionne told the NewsHour. “As he said to Bob Kuttner — he was fighting it all the time. ”

“It’s also a victory for [National Security Advisor H.R.] McMaster and a steadier foreign policy, although possibly a more hawkish one,” Dionne said.

But “I think it would be a mistake to assume the administration is going to take a markedly different turn now — it’s reflected the character of Donald J. Trump more than anyone else, and that’s not changing,” says the National Review’s Ramesh Ponnuru.

“As controversial and problematic Bannon is, he’s leaving for basically petty reasons: the president thought he was getting too much credit,” he told NewsHour. “When Spicer left, it wasn’t because he told one lie too many, it was because he didn’t want to report to someone higher. It’s always something petty,” he added.

PBS NewsHour’s Lisa Desjardins and Ellis Kim reported for this story.