WASHINGTON — Uncertainty surrounds the leadership of the Pentagon and military branches as top officials vacate their positions on Monday, coinciding with President-elect Donald Trump’s inauguration.

As of Friday, the incoming administration hadn’t publicly named an acting defense secretary. Military chiefs of the Army, Navy, and Air Force are prepared to temporarily assume the roles of acting service secretaries—an unusual measure—due to a lack of civilian appointees.

As is standard procedure, all current political appointees will depart at noon EST on Inauguration Day, leaving numerous key defense posts vacant, many requiring Senate confirmation. This includes the top Pentagon position, all three service secretaries, their deputies, and senior policy staff.

The Senate Armed Services Committee is scheduled to vote Monday on Trump’s defense secretary nominee, Pete Hegseth, though a full Senate vote may be delayed. Consequently, a temporary leader from the Biden administration may be necessary.

Regarding the service secretaries, while subject to change, the Trump team is reportedly considering Gen. Randy George, Army chief of staff, for the Army’s temporary leadership. Gen. David Allvin (Air Force) and Adm. Lisa Franchetti (Navy) are also prepared to step in if needed.

Sources, speaking anonymously to discuss internal matters, reveal that many senior Biden administration officials are hesitant to join the incoming Trump administration, citing concerns over potential policy changes they might be required to implement.

Typically, only presidential appointees confirmed by the Senate serve as defense or service secretaries, including in acting capacities during transitions. Alternatively, Trump could appoint a confirmed member of the Biden administration from another agency.

While civilian control of the military is paramount, the law allows for the temporary assignment of military chiefs—all Senate-confirmed—to civilian leadership roles. Though uncommon, this occurred over 30 years ago.

Retired Marine Corps Reserve General Arnold Punaro cites the 1993 example of Adm. Frank Kelso, who served as acting Navy secretary under President Clinton due to a lack of civilian volunteers.

Punaro, a former Senate Armed Services Committee staff director and long-time advisor to nominees, notes the infrequency of this practice and the inherent challenges of military personnel simultaneously fulfilling civilian and military roles.

Historically, the transition of defense leadership has been a smooth process.

Four years prior, David Norquist, Trump’s deputy secretary of defense, served as acting secretary for two days between President Biden’s inauguration and Lloyd Austin’s Senate confirmation.

President Obama retained Robert Gates, his Republican predecessor’s defense secretary, in 2009.

In 2017, Jim Mattis, Trump’s first-term nominee, was confirmed on Inauguration Day.

Past administrations have employed varying approaches, sometimes retaining individuals temporarily. In one recent case, service comptrollers filled acting secretary roles, given the upcoming budget process, prioritizing less politically-charged individuals.

This year’s transition is further complicated by Trump and Hegseth’s stated intention to remove “woke” generals from the Defense Department, potentially impacting the military leadership structure.

During his confirmation hearing, Senator Elissa Slotkin questioned Hegseth about potentially firing Gen. CQ Brown, the Joint Chiefs chairman. Hegseth responded that all senior officers would be evaluated based on merit, standards, and adherence to lawful orders.

Hegseth previously advocated for Brown’s dismissal. Conservative groups have circulated lists of generals they believe should be removed for supporting diversity initiatives. If Brown is removed, the vice chairman would assume leadership until a new chairman is confirmed.

—Associated Press writer Tara Copp contributed to this report.