Sources told CNN that Bannon's ouster had been in the works for two weeks and a source said that while Bannon was given the option to resign, he was ultimately forced out. White House press secretary Sarah Huckabee Sanders confirmed Bannon's departure, but claimed the decision for him to leave was mutual.

"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," Sanders said in a statement.

The President has privately stewed over Bannon in recent days, including Thursday night from his golf course in New Jersey. He was furious with his chief strategist after he was quoted in an interview with the American Prospect contradicting Trump on North Korea and asserting that Bannon was able to make personnel changes at the State Department.

On Saturday morning, however, the President tweeted out his thanks to Bannon: "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."

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 — Donald J. Trump (@realDonaldTrump) August 19, 2017

Bannon's exit comes just seven months after Trump took office and three weeks after retired Gen. Kelly took over as chief of staff, looking to instill order in a chaotic White House beset by internal divisions, staff infighting and a storm of controversies.

Bannon's exit meant one of the White House's most controversial staffers, the man generally perceived as the driving force behind Trump's "nationalist" ideology, would no longer be at the center of the Trump universe.

Bannon joined Trump's campaign last year, moving from the sidelines as one of Trump's top cheerleaders to a position atop his campaign apparatus.

He did not travel with the President during the first week of what White House officials described as a "working vacation" at Trump's golf course in Bedminster, New Jersey. Instead Bannon remained in Washington where he worked out of a temporary office in the Eisenhower Executive Office Building as the West Wing underwent renovations.

Bannon was supposed to be fired two weeks ago, a White House official told CNN's Jeff Zeleny, but it was put off.

CNN reports the President equivocated after an initial plan was to fire Bannon and then-Chief of Staff Reince Priebus at same time, the official says, because Rep. Mark Meadows, the influential chairman of the conservative House Freedom Caucus, and others urged Trump to keep him on board.

The interview this week was enough for Meadows to change his view, a person close to him says.

What Bannon is thinking

After his firing Friday, Bannon spoke to The Weekly Standard , making a pointed case that the Trump presidency that his brand of populist, right-wing conservatives helped make possible is now "over."

"We still have a huge movement, and we will make something of this Trump presidency," Bannon told The Weekly Standard. "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."

The question now is whether Bannon will be an ally or a thorn in the side of the Trump administration outside the White House, where he has apparently already returned to his role as head of Breitbart, the right-wing news site he ran until he joined Trump's campaign a year ago.

However that unfolds, Bannon is expected to remain tightly connected to the billionaire conservative father-daughter pair Robert and Rebekah Mercer, who are major investors in Breitbart News and top Trump donors.

Bannon returned to the role of executive chairman of Breitbart News and chaired the evening editorial meeting, the publication's White House correspondent reported Friday evening.

Both Bannon and Trump spoke with the Mercers in recent days, a White House official said.

A White House ally who has talked to Bannon said the outgoing chief strategist does not want to go to war with Trump. Bannon is making that clear to close associates in response to Breitbart editor Joel Pollak tweeting #WAR.

"That's not where Steve's head is at," this source said. "He's been fighting for the exact same things that the President has been fighting for."

This source quoted Bannon as saying "I want (Trump) to succeed."

Still, as his firing appeared increasingly likely, Bannon downplayed concerns about being booted from the White House and argued that he would be a more powerful force from the outside, sources close to Bannon said.

He has privately told associates he would return to his "killing machine" -- Breitbart -- if he was forced to leave for the White House and has said he would be able to more easily target some of his White House rivals -- like chief economic adviser Gary Cohn and national security adviser H.R. McMaster -- from the outside, the sources said.

Bannon has also worked in recent weeks to put the pieces in place for his agenda to live on without him at the White House, working on hardline trade initiatives in his final weeks.

After pushing the President to start the process of investigating Chinese trade abuses, Bannon also laid the groundwork for a series of aggressive trade actions designed to impose a harder line against China, the sources said.

In his final days at the White House, Bannon was continuing to work up schedules for the rollout of trade initiatives that would come in September, long after he expected to be forced from the White House, the sources said.

"We're going to run the tables on these guys," Bannon told The American Prospect in an interview earlier this week.

A quick and contentious tenure

Bannon's turbulent White House tenure was marked by controversy.

In the administration, Bannon frequently butted heads with other advisers to the President, feuding with son-in-law and senior adviser Jared Kushner, chief economic adviser Cohn and other more moderate members of the President's administration whom Bannon branded as "globalists."

Bannon was often suspected by colleagues of badmouthing them to reporters and he rubbed colleagues the wrong way by attempting to ramrod his ideological positions.

"Steve was never a team player," a senior administration official said.

Bannon viewed himself as the populist defender of Trump's campaign promises in the White House, working daily to tick off items from the list of promises that hung on the walls of his West Wing office.

Bannon focused especially on pushing a hardline trade agenda, recently working to cue up a series of trade policies to aggressively target Chinese foreign trade abuses and work toward rebalancing the trading relationship between the US and China.

Bannon was an influential voice inside the White House, feeding and encouraging Trump's nationalist and populist instincts.

In the process, he garnered an infamous reputation as a puppet master pulling the strings in the Oval Office, with pop culture portrayals ranging from the moniker "President Bannon" to his depiction as the grim reaper on "Saturday Night Live." Those portrayals -- coupled with a Time Magazine cover that declared him "the great manipulator" -- often angered Trump, who chafes at being outshined.

But the reality is that while Bannon was an influential figure at Trump's side, he was hardly the all-powerful aide so many sought to portray him as.

He did not always come out victorious in his feuds with fellow White House aides and Trump did not always heed his counsel.

Still, Bannon served as a daily reminder to Trump of his populist campaign promises and his bellicose political instincts. Bannon's rivals in the White House argued that he encouraged the President's worst instincts, while his allies said he was keeping the soul of Trump's movement alive.

The fiery chief strategist also led the charge against proposals by national security officials to deepen US military involvement in Afghanistan, feuding vocally during meetings of the National Security Council with McMaster and working behind the scenes to water down hawkish proposals for troop increases and a longer-term US military commitment.

The President is meeting Friday with members of his national security team at Camp David to consider options for the future of the US war in Afghanistan as he nears a decision, but Bannon is not there -- and was not scheduled to be, based on a list of attendees the White House sent out Friday morning.

This story is breaking and will update with additional news.

CORRECTION: This graphic has been updated to reflect Shaub's duration on staff for the Trump administration. He was on staff 180 days.

CLARIFICATION: This graphic has been updated to clarify Scaramucci's and Comey's duration on staff based on the their start and end dates. They stayed on staff 11 days and 110 days, respectively.