US President Donald Trump ousted his beleaguered chief of staff Reince Priebus on Friday, replacing him with Homeland Security Secretary and former general John Kelly, who will bring a military bearing to the job.

Since entering the White House six months ago, Trump has parted company with his national security advisor, deputy national security advisor, FBI director, press secretary, communications director, acting attorney general, deputy chief of staff and now chief of staff, a turnover of top officials that is unparalleled in US political history.

Priebus has been under fire for months, seeing one White House ally after another resign or leave, culminating in the departure of press secretary Sean Spicer a week ago.

His exit appeared inevitable when Trump did not intervene as his new communications director Anthony Scaramucci publicly described Priebus as a “paranoid schizophrenic” in a foul-mouthed tirade that also saw him savage another top Trump aide.

Trump announced the switch on Twitter as he landed in Washington after a day trip, on which he was accompanied by both Priebus and Scaramucci.

“I am pleased to inform you that I have just named General/Secretary John F Kelly as White House Chief of Staff,” Trump tweeted.

“He is a Great American… and a Great Leader. John has also done a spectacular job at Homeland Security. He has been a true star of my Administration.”

Kelly is a battle-hardened veteran of three tours in Iraq.

As Homeland Security secretary, Kelly took the lead on some of Trump’s most controversial policies. They include Trump’s executive orders suspending the admission of refugees and temporarily barring visitors from several Muslim-majority nations.

Kelly has stood up to Congress, another facet of his history that Trump might find attractive.

In April, he challenged lawmakers critical of the aggressive approach to immigration enforcement to either change the laws or “shut up.”

White House spokeswoman Sarah Huckabee Sanders said discussions about Priebus’ departure had been taking place for weeks.

Priebus later said he resigned on Thursday, but referring to his departure admitted that he and Trump “talked all the time about this subject.”