WASHINGTON — Nearly 16 months after he walked across a Lafayette Square aggressively cleared of protesters with then President Donald J. Trump, Gen. Mark A. Milley, the chairman of the Joint Chiefs of Staff, is still trying to make amends.
He has apologized in a video that infuriated Mr. Trump.
He has stood up against Republican lawmakers who accused the Pentagon of being too “woke,” issuing a historically expansive rebuke that referenced Mao and Lenin before a head-shaking Representative Matt Gaetz, Republican of Florida.
And he has talked, to a succession of authors, about his efforts during the last tumultuous months of the Trump administration to protect the military and American democratic institutions from a president who was searching for avenues to remain in power. Those moves, as described in one book, culminated with General Milley twice calling to reassure his Chinese counterpart and extracting promises from the military chain of command not to launch a nuclear weapon on Mr. Trump’s orders without first alerting him.
In so doing, General Milley has prompted demands from some Republicans to resign and rekindled discussions about the ways that Mr. Trump put the military where the country’s founding fathers said it was not supposed to be: at the center of politics.
On Tuesday, General Milley will appear in what could be the most significant televised congressional hearing involving senior military leaders since Gen. David H. Petraeus was grilled by lawmakers on the stalled war in Iraq in 2007.
Halfway through his four-year term as the nation’s top military officer, General Milley is certain to face sharp questions about another contentious topic: Afghanistan, including his advice to President Biden not to withdraw all U.S. troops from the country. (Defense Secretary Lloyd J. Austin III, who will also be at the hearing, offered the same advice.)
The general is also likely to be asked about declaring a U.S. drone attack in Kabul last month “a righteous strike” even after military officials said they were investigating reports of civilian casualties. The Pentagon acknowledged a week later that the strike was a tragic mistake, killing 10 people, including seven children. General Milley tacitly conceded that he spoke too soon, calling the error “heart-wrenching.”
In normal times, the tumultuous Afghanistan withdrawal punctuated by the tragic errant drone strike would be enough, by themselves, to dominate any congressional hearing with senior Pentagon leaders. But the recent revelations that General Milley may have inserted himself into the chain of command to check Mr. Trump’s capability to launch a nuclear strike raise questions about the limitations of a doctrine traditionally viewed as sacred: civilian control of the military.
Today’s polarization means that anything that smacks of either a critique or an endorsement of Mr. Trump is suspect. So now, a little over a year after Mr. Trump’s critics were furious with General Milley for walking across Lafayette Square during racial justice protests, Mr. Trump’s supporters are angry at the general for telling House Speaker Nancy Pelosi in the days after the Jan. 6 Capitol riots that he agreed with her when she called Mr. Trump “crazy.”
The dichotomy highlights an existential question that no senior official has confronted publicly: What is the military’s duty in curbing the unilateral power of a reckless commander in chief?
“At the end of the day, we want to adhere to normal rules and processes, because that’s important to sustaining democracy,” said Risa Brooks, professor of political science at Marquette University and an adjunct scholar at West Point’s Modern War Institute.
But, she added, “Look, the Constitution is not a suicide pact. If you have someone in power who is dead set at taking that down, then you’re responsible for calling that out. The Milley situation encapsulates that.”
Both Democrats and Republicans are expected to demand answers, and a pithy quote in response could land the general in hot water — with Congress or the White House. “This is a crucial time for Milley,” said Jeffrey J. Schloesser, a retired two-star Army general who as commander of U.S. forces in eastern Afghanistan from 2008 to 2009 was General Milley’s boss.
While General Milley leads the Joint Chiefs, he is not in the military chain of command — the line of authority along which orders are passed. But he is in the chain of communications when it comes to deploying troops or ordering strikes, and he will most likely tell lawmakers it his job to ensure that proper protocols and procedures are followed when carrying out any lawful orders from the commander in chief.
This article is based on interviews with nearly two dozen current and former Pentagon and military colleagues, other government officials and independent military analysts, some of whom were granted anonymity to speak candidly about the general.
Brash yet intellectual, General Milley’s classic straight-out-of-central casting demeanor appealed to Mr. Trump when, in 2018, the four-star Army general walked into the Oval Office for what was supposed to be an interview to be the top American commander across the Atlantic — supreme allied commander for Europe. During the meeting, the president asked whether the chairman of the Joint Chiefs of Staff job was better. General Milley went for the top prize.
On June 1, 2020, just eight months after he was sworn in as the senior military adviser to the president, General Milley, in the camouflage uniform he wears every day to work, walked across Lafayette Square alongside Mr. Trump and into a political firestorm. Troops had used chemical spray to clear the area of protesters so that the president could walk, untroubled, through the park to St. John’s Church, where he held up a Bible and posed for photos.
The backlash was instant. “Milley (he’s a general !?!?) should not have walked over to the church with Trump,” Michael Hayden, the retired Air Force general who has directed both the National Security Agency and the C.I.A., said on Twitter, noting that he “was appalled to see him in his battle dress.”
General Milley has agonized about that walk ever since, colleagues say. In the hours after, he talked to National Guard troops and protesters on the streets of downtown Washington. In the days after, he wrote a letter to troops reminding them that the military is supposed to protect the right to freedom of speech, and added a handwritten codicil, some of it straying outside the margins: “We all committed our lives to the idea that is America — we will stay true to that oath and the American people.”
In the weeks after, he recorded his apology. “I should not have been there,” General Milley said in the video. “My presence in that moment and in that environment created a perception of the military involved in domestic politics.”
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But he didn’t stop there. Lafayette Square and Mr. Trump’s efforts to invoke the Insurrection Act so that he could deploy troops onto the streets of American cities against Black Lives Matter protesters were eye-opening for General Milley, his friends and colleagues at the Pentagon say. With a presidential election coming up, the general told friends that one of his biggest goals was to get the country through the next few months intact, and to blunt efforts by Mr. Trump to use the military for his own political gain.
It was in those last months of the Trump presidency that General Milley took a series of extraordinary steps. Upon learning from intelligence sources that Beijing was worried about what Mr. Trump might do, he called his Chinese counterpart, twice, and reassured him that the United States had no plans to attack China. He settled on a plan, with then Defense Secretary Mark T. Esper, to hold back the promotions of two female generals to top positions until after Jan. 20 over fears that Mr. Trump preferred white men for senior military jobs. He convened a meeting with top commanders to remind them of the procedures for launching a nuclear weapons, telling them that he needed to be alerted immediately if such an order came from Mr. Trump.
General Milley’s supporters say that he defended the country’s interests. “Milley has navigated some difficult waters reasonably well, waters that he shouldn’t have had to have been in,” said Peter D. Feaver, a professor of political science at Duke University who has studied the armed forces.
But his supporters also say that it might have been smarter if he had remained silent about what he did. Instead, he talked, at length, to a slew of authors writing books about the Trump presidency, infuriating Republicans in particular.
“I have yet to read a book about policymaking in the Trump administration that doesn’t quote General Milley directly, or quote friends of Milley casting his actions in the best possible light,” said Kori Schake, who directs foreign and military policy studies at the conservative American Enterprise Institute and served in the Pentagon under President George W. Bush. “That lack of discretion is injurious to civil military conversations.”
Defense Department officials said General Milley spoke at length to the Washington Post reporter Bob Woodward for his recent book “Peril,” written with Robert Costa. General Milley’s friends worry that more Trump books are on their way that could well feature more interviews with the loquacious general.
“General Milley is a battle-hardened officer grounded by intellect and probity, but sometimes his passion for the mission, his self-confidence and his forcefulness irritate civilian leadership,” said Richard V. Spencer, the former Navy secretary who was ousted by Mr. Trump over a disagreement about a war crimes case involving a Navy SEAL. “He has to be careful not to overstep his role as chairman, which I never witnessed in my time working with him. But he needs to be more restrained than he has been.”
General Milley’s friends acknowledge that a lot of his disclosures to book writers have been about redemption after that walk across Lafayette Square with Mr. Trump. “He has a bruised ego from June 1, and he cannot get over it,” said one Biden administration official, who is a fan of General Milley.
But even some of General Milley’s critics say he should be commended for holding the country’s natural security apparatus together at a time of unprecedented stress. Not since Harry S. Truman appointed Gen. Omar Bradley as the country’s first chairman of the Joint Chiefs of Staff in 1949 has a senior military adviser to the president been so directly at the nexus of competing political forces in the country, let alone dealt with a commander in chief so disinterested in preserving the country’s democratic institutions.
For General Milley, “there’s more and more pressure, a higher likelihood that things that are not politicized get politicized,” said Adm. Mike Mullen, who was chairman of the Joint Chiefs of Staff under President Barack Obama. “Even the Weather Service got politicized under Trump.”
“It’s the electricity that lives in the environment,” Admiral Mullen said in an interview. “And that’s where Milley lives.”