Lawmakers signed off on Dan Caine's nomination and promotion to four-star general in an early morning vote of 60 to 25 ahead of a two-week recess.

Trump's administration has dismissed a series of senior officers as part of a rare and major shakeup of top US military leadership that began shortly after he returned to office in January.

Democrats have sharply criticized the firings -- including of the previous Joint Chiefs chairman, general Charles "CQ" Brown -- accusing Trump and Defense Secretary Pete Hegseth of seeking to ensure the military is led by people loyal to the president.

Caine sought to allay such concerns about his nomination during his confirmation hearing last week, pledging that he would "continue the traditions and standards of my oath of office and my commission as a nonpartisan leader who will always strive to do the right thing."

He said that guarding against politicization of the military "starts with being a good example from the top and making sure that we are nonpartisan and apolitical and speaking the truth to power every day."

"The nation and the Constitution all require a nonpartisan military," said Caine, who as a retired lieutenant general was a highly unusual candidate for the top military post.

Nominees for chairman of the Joint Chiefs must have served as the head of a military branch, as leader of a combatant command or as vice chairman -- none of which Caine has done -- but the president can waive that requirement.

- Top officers fired -

Caine has served in positions including associate director for military affairs at the CIA as well as in various operational and staff roles, and flew more than 150 hours in combat as an F-16 pilot -- an aircraft in which he has logged more than 2,800 hours in total.

Trump has described him as "an accomplished pilot, national security expert, successful entrepreneur, and a 'warfighter' with significant interagency and special operations experience."

The president apparently became enamored of Caine after meeting him in Iraq during his first term, where Trump said the general told him that his nickname was "Razin."

"I said, wait a minute, your name is Razin Caine? I love you, I've been looking for you for five years... this is what I want," Trump told an investor forum in February.

But Trump has soured on the country's top military officer before. General Mark Milley began serving as chairman of the Joint Chiefs during the president's first term but later clashed with him and was stripped of his security detail and security clearance in retirement this year.

The president fired Brown in February, less than two years into his four-year term as chairman, which began under Trump's predecessor Joe Biden -- a move that cleared the way for Caine's nomination.

Other senior officers dismissed this year include the heads of the Navy and Coast Guard, the general who headed the National Security Agency, the vice chief of staff of the Air Force, a Navy admiral assigned to NATO, and three top military lawyers.

Hegseth has insisted the president is simply choosing the leaders he wants, but Democratic lawmakers have raised concerns about the potential politicization of the traditionally apolitical US military.