Ricky Buria, the defense secretary’s de facto chief of staff, is a rare Biden administration holdover and an internal critic of Vice President JD Vance’s “wackamamie crazy” and “isolationist” views — who has also slammed President Trump’s use of the military for immigration enforcement as “dumb.”

Buria, 43, is also considered “incredibly intelligent and hardworking,” has fashioned himself as a China hawk and is seen by Hegseth as an effective administrator who keeps the office running smoothly — but the White House has blocked him from a permanent chief of staff appointment due to concern about his alignment with the commander-in-chief.

“There is an ideological component to this,” said one Buria critic. “Hegseth is elevating a Democrat who does not share the vice president or the president’s worldview and who weaponized his position to push out internal rivals, including people who had very strong histories of being supporters of the MAGA agenda.”

Buria’s elevated status has triggered a brouhaha among factions close to Trump, who has had aides hold varying views throughout his terms in office — while often changing his own in response to circumstances.

Trump often vacillates between denouncing military action abroad and ordering its use in specific instances — and Buria has positioned himself on one flank, while those with whom he’s clashed internally have diverse points of view.

“He is more interventionist than most of the people in Trumpworld,” the Buria detractor added. “But everyone wants to distill this story down to one neat narrative. Yeah, Ricky didn’t like the VP’s worldview, I think that’s an element. But Ricky’s ascendency isn’t a part of that clash.”

Though the Trump White House recently turned down Hegseth’s request to make Buria his top adviser, he nonetheless continues as right-hand man to the defense secretary — who last month fired, with Buria’s encouragement, three top aides including well-known non-interventionist Dan Caldwell, who had served as a senior adviser to the defense secretary.

The Post spoke to eight sources inside or close to the Pentagon and White House to investigate Buria’s rapid ascent from serving Biden’s defense secretary, Lloyd Austin, as a junior military aide — a prestigious but largely bag-carrying role — to reaching the top of Trump’s Defense Department’s leadership.

Buria’s criticism of the administration he serves has not previously been reported, but is well known within both the Pentagon and White House — and one source speculated that his candor may have been the result of not realizing that he would emerge unscathed from last month’s purge.

“There was absolutely no withholding of his personal sentiments on any of this stuff,” one source said. “He would talk about the ‘wackamamie crazy’ of [Vance] and the New Right. He was a military officer, which makes it even worse.”

Buria, who put in his paperwork to retire from the Marine Corps last month to allow for a possible political appointment that would cement his current role, in February condemned Trump’s decision to use military aircraft to repatriate migrants and to use Guantanamo Bay to facilitate deportations — declaring it a “dumb waste of money” — three independent sources said.

“He hated and loathed the border mission,” one person said. “He thinks it’s a waste of money, resources and time and we got to focus on China — China, China, China … He never said ‘China’ once the first couple weeks.”

The extent of Buria’s influence on implementation of administration policy is unclear and Trump has stood by Hegseth, who is viewed as being on the more hawkish wing of the administration while maintaining good personal relationships with other key figures, including Vance.

“He hated and loathed the border mission,” one person said. “He thinks it’s a waste of money, resources and time and we got to focus on China — China, China, China … He never said ‘China’ once the first couple weeks.”

Two sources said Buria specifically condemned Vance’s views on foreign policy after the VP expressed internal opposition to airstrikes on Yemen’s Iran-backed Houthis in mid-March, a stance which was reported by Atlantic magazine editor-in-chief Jeffrey Goldberg after he was mistakenly added to a Signal chat that included administration officials.

Days earlier, on March 5, Buria clashed with Vance’s team during a trip to the Mexican border when the VP’s staff denied Buria’s repeated demands to be included on a helicopter flight with Vance and Hegseth despite being told the manifest was full and there was no space for him, four sources said.

Hegseth’s tenure at the Pentagon has been defined by a series of reports alleging a lax approach to information security — including that he discussed sensitive work with family members and used an insecure internet line to connect to Signal.

The Post’s sources described additional operational security concerns.

Buria’s wide-ranging advisory and logistical roles include managing Hegseth’s personal cellphone, according to three sources, two of whom said they saw him flout security protocols by bringing it into the secretary’s office — which is deemed a Sensitive Compartmented Information Facility, where personal devices are not allowed.

One source said they personally witnessed Buria bring Hegseth’s phone into the SCIF “at least a dozen times.”

A second person scoffed that such behavior is more common within the US government than the public would know.