Donald Trump's new chief of staff faces a tough battle to bring discipline to an unruly White House, according to Washington observers, as the president attempts to overhaul an administration prone to leaking and internal squabbling.
John Kelly, a retired four-star Marine Corps general, will start his new job on Monday, replacing Reince Priebus, whose establishment credentials meant he never gelled with Mr Trump's unconventional team.
The decision was announced on Friday evening in characteristic fashion – with an unexpected tweet.
It ends months of private criticism that Mr Priebus was too weak for the job, presiding over a fractious White House and unable to drive the president's agenda.
In his place, the square-jawed retired general – a veteran of three tours of Iraq and father of a son who was killed in Afghanistan – has won presidential praise for his firm hand as the head of the department of homeland security.
Mr Kelly is also a true believer. He warned of the threat of terrorists crossing America's southern border long before Mr Trump proposed his wall and this year backed the president's travel ban on seven – and then six – Muslim nations.
"He is a Great American and a Great Leader," wrote Mr Trump. "John has also done a spectacular job at Homeland Security. He has been a true star of my administration."
But if his job is to impose order, then his biggest challenge might be to rein in his boss.
Mr Trump took to Twitter on Saturday morning to express his frustration with his own party's failure to pass a bill repealing ObamaCare.
"Republicans in the Senate will NEVER win if they don't go to a 51 vote majority NOW. They look like fools and are just wasting time," he wrote in the sort of tirade that makes critics accuse him of not understanding how the Senate works or how the constitution provides checks and balances on presidential power.
Mr Kelly's supporters say he has the experience of managing big organisations and the leadership qualities needed for the role.
He is one of three senior former or serving generals to have won key posts in Mr Trump's administration – the others being HR McMaster as national security adviser and Jim Mattis as defence secretary.
Rich Galen, a Republican strategist, said the appointment was typical of Mr Trump.
"He loves generals, he loves people who rose to the top of their profession – whether it is building golf courses or hedge funds or oil and gas companies or the army," he said.
However, he added that a man who has spent his entire career in the armed forces may struggle to cope with Mr Trump's chaotic management style. Senior figures such as Steve Bannon, chief strategist, and Anthony Scaramucci, director of communications, bypass the usual chain of command and instead report directly to the president.
Jack Jacobs, a retired army colonel, told MSNBC Mr Kelly's impressive qualities of integrity and patriotism would count for little.
"At the end of the day, Gen Kelly is either going to have to accept a diminished role as chief of staff or he's going to be frustrated and he's going to have to leave," he said.
The president has made no secret of how he likes to have imposing military figures at his side. And, at 67, Mr Kelly is close to his own age.
In contrast, friends of the president let it be known that he considered Mr Priebus to be "weak" and blamed him for the way his legislative agenda stalled in congress.
Mr Priebus's position as an establishment insider also created friction with Mr Trump's closest advisers.
He had hoped to remain in the job for a year but served only 189 days, the shortest tenure in modern history.
"I would like to thank Reince Priebus for his service and dedication to his country," added Mr Trump in a later tweet. "We accomplished a lot together and I am proud of him!"
Mr Priebus gambled his political career when he became one of a small number of senior Republicans to join Mr Trump's band of relatives, millionaires and populist outsiders last year.
However, it meant he cut an increasingly tragic figure in the West Wing, according to insiders, as he struggled to cope with an unpredictable boss.
The end began last Friday when Mr Trump announced the appointment of Mr Scaramucci, a wealthy hedge fund manager, as director of communications despite the objections of Mr Priebus.
It meant the press operation – until then the domain of the chief of staff's small band of Republican apparatchiks – would fall into the hands of one of Mr Trump's brash New York friends.
The pivotal moments arrived on Thursday, firstly in the morning when Mr Scaramucci took to CNN and demanded that Mr Priebus come clean on whether he was responsible for White House leaks.
Worse followed when Ryan Lizza, a reporter with the New Yorker magazine, published details of an expletive-ridden conversation with Mr Scaramucci in which he called Mr Priebus "paranoid".
Mr Priebus said he offered his resignation on Thursday night, soon after the rant became public, after being told days earlier that a shake-up was coming.
In an interview with CNN, he said the president was entitled to hit the "reset button".
"This is not a situation where there's a bunch of ill will," he said. "I think the president wanted to go in a different direction – I support him in that."
