WASHINGTON -- President-elect Donald Trump's^[1] choice for defense secretary is still up in the air, but it is a sure bet he will look to reshape the Pentagon and pick a loyalist following his tumultuous first term. Five men held the job as Pentagon chief only to resign, be fired or serve briefly as a stopgap.

While he has yet to announce a decision, the names of potential Pentagon chiefs stretch from the well-known -- such as Rep. Mike Waltz of Florida -- to an array of former administration loyalists, including retired Lt. Gen. Keith Kellogg, who held national security posts during Trump's first term.

Former Secretary of State Mike Pompeo had been floated, but Trump said on social media Saturday that Pompeo would not be joining the new administration.

Some decisions may linger for days as candidates jostle for attention and officials wait for the final results from House races^[2], weighing whether Republican lawmakers can be tapped or if others are a safer pick to avoid a new election for an empty congressional seat.

"The choice is going to tell us a lot about how he will deal with the Pentagon," said Mark Cancian, senior adviser with the Center for Strategic and International Studies and a retired Marine colonel.

He said someone like Waltz -- a former Army^[3] officer and Green Beret -- with a deep military background may not be as dramatic of a change as others who may be viewed as stronger Trump loyalists.

With a number of top jobs at the State Department, National Security Council and Defense Department up for grabs, Trump is expected to lean toward those who back his desire to end U.S. involvement in any wars^[4], use the military to control the U.S.-Mexico border^[5] and take a hard line on Iran^[6].

The key test, however, will be loyalty and a willingness to do whatever Trump wants, as he seeks to avoid the pushback he got from the Pentagon the first time around.

Trump's relationship with his civilian and military leaders during those years was fraught with tension, confusion and frustration, as they struggled to temper or even simply interpret presidential tweets and pronouncements that blindsided them with abrupt policy decisions they weren't prepared to explain or defend.

Time after time, senior Pentagon officials -- both in and out of uniform -- worked to dissuade, delay or derail Trump, on issues ranging from his early demand to prohibit transgender troops from serving in the military and his announcements that he was pulling troops out of Syria^[7], Iraq and Afghanistan^[8] to his push to use troops to police the border^[9] and stem civil unrest on the streets of Washington^[10].

In his first administration, Trump hewed toward what he considered strong military men and defense industry executives. Initially enamored with generals, Trump over time found them to be not loyal enough.

"He soured on them," Cancian said. "They were not as pliable as he had thought. ... I've heard people speculate that maybe the chairman would be fired. So that's something to watch."

Air Force^[11] Gen. CQ Brown, took over as chairman of the Joint Chiefs of Staff in October 2023 for a four-year term, but military leaders serve at the pleasure of the president. Brown, a combat pilot and just the second Black officer to serve as chairman, spoke out after the police killing of George Floyd, describing the bias he faced in his life and career.

Trump also is expected to choose someone as defense secretary with disdain for equity and diversity programs^[12] and less likely to counter his plans based on limits laid out in the Constitution and rule of law. But he also may well push for increased defense spending, at least initially, including on U.S. missile defense.

A key overriding concern is that Trump will select someone who won't push back against potentially unlawful or dangerous orders or protect the military's longstanding apolitical status^[13].

On Thursday, Defense Secretary Lloyd Austin raised that red flag. In a message to the force, he said the U.S. military stands ready to "obey all lawful orders^[14] from its civilian chain of command," adding that troops swear an oath to "support and defend the Constitution of the United States."

He echoed retired Army Gen. Mark Milley's pronouncement during a speech as he closed out four years as chairman of the Joint Chiefs.

"We don't take an oath to a king or a queen or to a tyrant or a dictator. And we don't take an oath to a wannabe dictator," Milley said. "We don't take an oath to an individual. We take an oath to the Constitution, and we take an oath to the idea that is America, and we're willing to die to protect it."

Trump's first defense chief, retired Marine Gen. Jim Mattis, learned quickly to stay off his boss' radar by largely eliminating press conferences that Trump could see.

Mattis and Milley, along with Trump's chief of staff John Kelly, a retired Marine general, and retired Marine Gen. Joseph Dunford, who also served as Joint Chiefs chairman, all worked quietly behind the scenes to temper some of Trump's decisions.

They stalled his demands that troops be quickly and completely withdrawn from Iraq, Syria and Afghanistan and managed to prevent the use of active-duty troops to quell civil unrest in Washington.

Two years in, Mattis abruptly resigned^[15] in December 2018 in frustration over Trump's national security policies, including a perceived disdain for allies and his demands to pull all troops out of Syria. Patrick Shanahan, the deputy defense secretary, took over as acting Pentagon chief but withdrew as the nominee six months later due to personal family problems that were made public.

Then-Army Secretary Mark Esper took over in an acting role, but he had to step aside briefly when nominated, so Navy^[16] Secretary Richard Spencer served as the acting chief until Esper was confirmed.

Esper was fired days after Trump lost the 2020 election^[17], largely because the president did not believe him to be loyal enough. Trump was especially angry over Esper's public opposition to invoking the two-centuries-old Insurrection Act to deploy active-duty troops in the District of Columbia during unrest following the police killing of George Floyd.

Trump named Christopher Miller, a retired Army officer who has been director of the National Counterterrorism Center, to serve as acting secretary and surrounded him with staunch loyalists.

That is the Pentagon that officials quietly say they expect to see in Trump's new administration.

WASHINGTON (AP) — The Defense Department will appeal a military judge's ruling^[1] that plea agreements struck by Khalid Sheikh Mohammed, the alleged mastermind of the Sept. 11, 2001 attacks, and two of his co-defendants are valid, a defense official said Saturday.

The ruling this past week voided Defense Secretary Lloyd Austin's order to throw out the deals^[2] and concluded that the plea agreements were valid. The judge granted the three motions to enter guilty pleas and said he would schedule them for a future date to be determined by the military commission.

The department will also seek a postponement of any hearing on the pleas, according to the official, who was not authorized to publicly discuss legal matters and spoke on condition of anonymity. Rear Adm. Aaron Rugh, the chief prosecutor, sent a letter Friday to the families of 9/11 victims informing them of the decision.

The ruling by the judge, Air Force Col. Matthew McCall, allowed the three 9/11 defendants to enter guilty pleas in the U.S. military courtroom at Guantanamo Bay, Cuba, and would spare them the risk of the death penalty. The pleas by Mohammed, Walid bin Attash and Mustafa al-Hawsawi would be a key step toward closing out the long-running and legally troubled government prosecution in the attacks that killed nearly 3,000 people.

Government prosecutors had negotiated the deals with defense lawyers under government auspices, and the top official for the military commission at Guantanamo had approved the agreements. But the deals were immediately slammed by Republican lawmakers and others when they were made public this summer.

Within days, Austin issued an order saying he was nullifying them. He said plea bargains in possible death penalty cases tied to one of the gravest crimes ever carried out on U.S. soil were a momentous step that should only be decided by the defense secretary.

The judge had ruled that Austin lacked the legal authority to toss out the plea deals.

The agreements, and Austin’s attempt to reverse them, have made for one of the most fraught episodes in a U.S. prosecution marked by delays and legal difficulties. That includes years of ongoing pretrial hearings to determine the admissibility of statements by the defendants, given their torture in CIA custody.

While families of some of the victims and others are adamant that the 9/11 prosecutions continue until trial and possible death sentences, legal experts say it is not clear that could ever happen. If the 9/11 cases ever clear the hurdles of trial, verdicts and sentencings, the U.S. Court of Appeals for the District of Columbia Circuit would likely hear many of the issues in the course of any death penalty appeals.

The issues include the CIA destruction of videos of interrogations, whether Austin’s plea deal reversal constituted unlawful interference and whether the torture of the men tainted subsequent interrogations by “clean teams” of FBI agents that did not involve violence.