Donald Trump abruptly fired the air force general CQ Brown Jr as chair of the joint chiefs of staff on Friday, sidelining a history-making Black fighter pilot and respected officer as part of a campaign to purge the military of leaders who support diversity and equity in the ranks.

The ouster of the second Black general to serve as chair of the joint chiefs comes three months after Pete Hegseth, the secretary of defense, outlined a plan for ridding the US military of diversity, equity and inclusion efforts during a podcast interview.

“First of all, you’ve got to fire the chairman of the joint chiefs,” Hegseth said during a November interview on the Shawn Ryan Show. “Any general that was involved, general, admiral, or whatever, that was involved in any of that DEI woke shit has got to go.”

Although Hegseth had been meeting regularly with Brown since the former Fox News host took over the top Pentagon job last month, he had openly questioned whether Brown had been named chair because he was Black. “Was it because of his skin color? Or his skill? We’ll never know, but always doubt – which on its face seems unfair to CQ. But since he has made the race card one of his biggest calling cards, it doesn’t really much matter,” Hegseth wrote in one of his books.

Brown had been praised, including by Time, for breaking racial barriers in the military and for his “warfighter” credentials. When he was sworn in as the air force chief of staff in 2020, during the first Trump administration, Brown acknowledged previous US military service members who had been denied advancement because of their race, Time reported. “It is due to their trials and tribulations in breaking barriers that I can address you today as the air force chief of staff,” Brown said.

In 2020, Trump himself had celebrated Brown’s confirmation on social media “as the USA’s first-ever African American military service chief” and noted that he had appointed him to that role. Brown’s experience as the former commander of Pacific air forces also meant he was “highly qualified to deter China and reassure allies in the Indo-Pacific”, Time noted that year.

“Under President Trump, we are putting in place new leadership that will focus our military on its core mission of deterring, fighting and winning wars,” Hegseth said in a statement after Brown’s firing, calling Brown a “thoughtful adviser”.

In a post on his social media platform Friday evening, Trump announced he would replace Brown with retired Lt Gen Dan “Razin” Caine, a retired military leader Trump said had been “passed over for promotion by Sleepy Joe Biden”.

Trump has repeatedly said that Caine impressed him during his first administration by assuring him that the Islamic State could be defeated very rapidly.

“Many so-called military ‘geniuses’ said it would take years to defeat Isis. General Caine, on the other hand, said it could be done quickly, and he delivered,” Trump posted on Truth Social on Friday.

At CPAC in 2019, Trump previously recounted a conversation in which he recalled asking Caine how fast the Islamic State could be defeated, and claimed that Caine had told him: “Sir, we can have it totally finished in one week,” a story that fact-checkers said at the time “didn’t add up”.

Caine, who is white, previously served as the associate director for military affairs at the Central Intelligence Agency, and had played a direct role in the air defense of Washington DC during the 11 September attacks. Caine recently became a venture partner at Shield Capital, a venture capital firm, which touted his experience as an entrepreneur who “co-founded and successfully exited multiple aerospace, defense, and healthcare companies”.

Trump’s announcements set off a period of upheaval at the Pentagon, which is already bracing for firings of civilian staff, a dramatic overhaul of its budget and a shift in US military deployments under Trump’s new America First foreign policy.

Trump also wrote that he would soon swap out five other high-level positions in an unprecedented shake-up of the leadership of the US military.

In a statement shortly after Trump’s Truth Social post, Hegseth clarified which five positions Trump appeared to be looking to fill, saying that he was “requesting nominations for the positions of Chief of Naval Operations and Air Force Vice Chief of Staff”, firing Adm Lisa Franchetti and Gen James Slife, who currently hold those positions.

“We are also requesting nominations for the Judge Advocates General for the Army, Navy and Air Force,” Hegseth added.

Caine’s military service includes combat roles in Iraq, special operations postings and positions inside some of the Pentagon’s most classified special access programs. However, it does not include key assignments that were identified in law as prerequisites for the job, with an exemption for the president to waive them if necessary in times of national interest.

The 1986 Goldwater-Nichols Act states that to be qualified, a chair must have served previously as either the vice-chair, as a combatant commander or a service chief – but that requirement could be waived if the “president determines such action is necessary in the national interest”.

Associated Press and Reuters contributed reporting