Defense Secretary Pete Hegseth, in a statement distributed shortly after Trump’s post, said he would dismiss five other senior officers, including Adm. Lisa Franchetti, the first woman to serve as chief of naval operations, and Gen. James Slife, a top Air Force officer.

“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.

Hegseth informed Brown, who was in Texas on Friday for a visit to the southwest border, that he was being removed before Trump’s announcement, said a U.S. defense official, speaking on the condition of anonymity to discuss the leadership shake-up. The vice chairman of the Joint Chiefs, Adm. Christopher Grady, is expected to serve as acting chairman until Caine can be confirmed.

Brown, a veteran pilot and battlefield commander whom Trump nominated during his first term in office to become the Air Force’s first African American chief of staff, was roughly 16 months into what was expected to be a four-year term. He was elevated to the military’s top position by President Joe Biden in 2023, making him the second Black man to hold the chairman’s job. Gen. Colin Powell was the first.

The firings appear to represent the most significant move yet in the administration’s emerging campaign to purge the Pentagon of what Hegseth has decried as “woke” policies and personnel and, despite the military’s role as a nonpartisan institution spanning administrations of both parties, to reshape its highest ranks.

In the weeks after he arrived at the Pentagon following a controversial confirmation process, Hegseth has moved quickly to dismantle diversity initiatives, which he has called “racist” and “illegal.”

At a Pentagon town hall this month, Hegseth said diversity initiatives have “served a purpose of dividing the force as opposed to uniting” the military. “The single dumbest phrase in military history is ‘our diversity is our strength,’” he said.

Before being tapped by Trump, Hegseth attacked senior officers by name, including Brown, whom he said was overly focused on diversity issues. He also criticized Franchetti, suggesting she was selected for the leadership post because of her gender.

The administration had previously fired another uniformed leader, Adm. Coast Guard Linda Fagan, for alleged leadership failures. The Coast Guard falls under the Department of Homeland Security.

In his post on Truth Social, Trump called Brown “a fine gentleman and an outstanding leader.”

“I wish a great future for him and his family,” the president said.

Sen. Roger Wicker (R-Mississippi), chairman of the Senate Armed Services Committee, thanked Brown for his service. “I am confident Secretary Hegseth and President Trump will select a qualified and capable successor for the critical position of Chairman of the Joint Chiefs of Staff,” he said in a statement.

But top Democrats decried the move. Sen. Jack Reed (Rhode Island), the committee’s ranking Democrat, said the dismissals appeared to mark an attempt to “purge talented officers for politically charged reasons, which would undermine the professionalism of our military and send a chilling message through the ranks.”

Rep. Adam Smith (Washington), the House Armed Services Committee’s top Democrat, labeled the moves a “Friday Night Massacre” that would weaken national security.

“All of this continues to play into the hands of Vladimir Putin and others working to exploit the weakness Trump continues to broadcast and undermine the military, our government, our national security interests, and democracy worldwide,” Smith said, referring to the Russian president.

Trump extolled Caine, a pilot who served in various Special Operations roles and at the CIA, as a “national security expert, successful entrepreneur, and a ‘warfighter’ with significant interagency and special operations experience.”

Caine’s selection bucks numerous norms. As a three-star general, he will vault numerous higher-ranking officers, including every current member of the Joint Chiefs of Staff. And unlike all of them, he has not commanded large formations of U.S. troops.

Caine is the first three-star general to be selected for a position typically held by four-star officers, said Arnold Punaro, a retired Marine Corps general who has informally advised numerous defense secretaries.

No chairman has taken the job without previously serving as a member of the Joint Chiefs of Staff since 1997, when President Bill Clinton selected Army Gen. Hugh Shelton, then the top officer in U.S. Special Operations Command. All of the other chairman since have he either served as the top officer in a branch of service, or as the Joint Chiefs vice chairman.

But Caine is not the first retired general to go on to become chairman of the Joint Chiefs of Staff. In 1962, President John F. Kennedy named Army Gen. Maxwell Taylor as chairman after recalling him to active duty the previous year to lead an investigation of the failed Bay of Pigs invasion on Cuba. Taylor had served as the top officer in the Army before retiring in 1959.

Caine also served in a part-time status in the National Guard from 2009 to 2016, according to his official biography, working as an entrepreneur and investor during that time.

When he returned to active duty in 2016, he became a general and served in several Special Operations roles, including as deputy commanding general of a joint ask force in Iraq during the campaign against the Islamic State.

From September 2019 to September 2021, he served as a two-star general and served as the director of special-access programs at the Pentagon, working with highly classified material and as an adviser to the defense secretary. He was promoted again in 2021, becoming the associate director for military affairs at the CIA.

Peter Feaver, a political scientist at Duke University, said Trump has the right to replace leaders he wants. But if there is a “good cause to replace them,” Feaver said, “he should explain that to build trust with the men and women who have pledged to put their lives in danger to follow his lawful orders.”

Feaver, who has advised military leaders on civil-military affairs, said the statements from Trump and Hegseth suggested that there were no merit-based causes.

“Removing them in this way will not make the military more lethal, but it could make the problem of politicization of the military that much harder to manage,” Feaver said.

Hegseth’s statement did not specify why Slife and Franchetti, along with the judge advocates general for the Navy, Army and Air Force, would be replaced.

Slife has served as the Air Force’s No. 2 officer since December 2023, and he had a series of jobs in Special Operations from 2017 to 2022. But he ran afoul of many Trump supporters after decrying the 2020 police murder of George Floyd, saying in a written message to airmen that it would be naive to think that institutional racism and unconscious bias do not affect us all.

“We can’t ignore it,” Slife wrote then. “We have to face it. And to face it, we have to talk about it.”