President Donald Trump said today that he had “essentially” fired Defense Secretary Jim Mattis last month because he was dissatisfied with Mattis’ performance in the top civilian job at the Pentagon.

His latest public criticism of Mattis, a retired Marine general, who resigned Dec. 20 after failing to persuade Trump to change his mind about withdrawing the 2,000 U.S. troops now in Syria, came at a time when the admiration Trump once regularly expressed for senior military officers has given way to anger at the retired officers who have questioned his character and condemned his performance in office now that they are civilians.

Once Trump treated the military with a level of reverence that he extends to few other U.S. institutions. Peppering his Cabinet with retired senior officers enabled him to allay the concerns within the Republican Party about his own lack of experience and preparedness for the role of president. He has spoken admiringly of “my generals” and talked about those who looked the part.

“They were like from a movie,” he said today, describing a recent Pentagon briefing. “Better looking than Tom Cruise, and stronger.”

But in the past few months, in ways big and small, some of the military’s most prominent figures, no longer inhibited by active duty, have spoken out against Trump in caustic terms, describing him as unfit for the presidency. And as in other situations where he has felt under attack, Trump has responded to criticism of his leadership by lashing out at his accusers.

After the president pulled the security clearance of John Brennan, former director of the CIA, retired Adm. William H. McRaven, a Navy SEAL who oversaw the raid that killed Osama bin Laden, wrote in The Washington Post that Trump has “embarrassed us in the eyes of our children.”

Gen. Stanley A. McChrystal, who commanded U.S.-led troops in Afghanistan from 2009 to 2010, said recently that Trump does not “tell the truth,” and has urged Americans to decide how much they are willing to tolerate from the president.

Gen. David Petraeus, a former director of the CIA, who was once seen as a potential administration official, recently said he would not work for Trump. And Gen. John Kelly, who stepped down this week as White House chief of staff, said in an exit interview that his tenure at the White House should be judged on what he prevented the president from doing.

Over the holidays, amid criticism of this abrupt announcement of withdrawing U.S. troops from Syria, Trump escalated his attacks, condemning the “failed generals” who had overseen Middle East engagements. He attacked McChrystal, who called Trump immoral in an appearance on ABC News over the weekend, writing on Twitter that he has a “big, dumb mouth” and is a “Hillary lover.” In a tweet weeks ago, he attacked McRaven for not killing bin Laden sooner.

“I think that we can expect more of this in the future now that the line’s been crossed,” said Peter R. Mansoor, a retired Army colonel and a former aide to Petraeus, who is now a professor at Ohio State University. “I’m not sure it’s healthy for civil-military relations.”

While Mattis’ resignation was the first over a major national security issue by a leading Cabinet member since 1980, when Cyrus Vance quit as secretary of state, his conflict with Trump was hardly the first time that there have been clashes between civilian and military officials.

In 2006, a number of retired military officers publicly rebuked Defense Secretary Donald Rumsfeld for his handling of the Iraq War. In 1993, President Bill Clinton was at odds with military officials over allowing gay men and lesbians in the military. And there was a hefty amount of distrust between President Barack Obama and military officials over the administration’s approach to Iraq and Afghanistan.

During the 2016 presidential campaign, Michael Flynn, a retired Army lieutenant general, led chants of “Lock her up!” about Hillary Clinton at the Republican National Convention, while John R. Allen, a retired Marine lieutenant general, as a speaker at the Democratic National Convention, questioned Trump’s ability to be the commander in chief.

But Peter Feaver, a former National Security Council official under Clinton and President George W. Bush who now teaches political science at Duke University, said Trump has taken these clashes to a new level.

“We’ve never had a president who was as insensitive to the norms and taboos” of the military, Feaver said. “People like McChrystal, people like McRaven and the others are responding to the president’s breaking of these taboos.”

“No American president has ever dared risk the American civil-military relationship for less cause or with such childish malice,” Tom Nichols, a professor at the Naval War College, wrote in The Atlantic after the McChrystal tweets.

In tweets of his own, McRaven defended McChrystal from Trump’s attacks.

“Stan McChrystal is one of the great generals of this generation and the finest officer I ever served with. He is a deep strategic thinker, tactically brilliant, with unparalleled personal courage. His leadership of special operations forces in Iraq and Afghanistan,” he wrote, “unquestionably saved the lives of thousands of American and allied troops, as well as countless civilians. No general I know has given more in the service of this country.”

Trump’s public criticism of Mattis, who was long considered “the adult” in the president’s Cabinet, was apparently provoked by his letter of resignation, in which Mattis outlined his own views about the value of alliances and wrote that the president was entitled to have a defense secretary whose views were “better aligned with yours.”

Mattis had originally said he planned to remain at the Pentagon through February to allow for an orderly transition. But after his letter received intense media coverage, Trump abruptly ordered him to leave the job as of Jan. 1.

“What’s he done for me? How has he done in Afghanistan? Not too good,” Trump said today at a Cabinet meeting that turned into an extended question-and-answer session with reporters. “I’m not happy with what he’s done in Afghanistan, and I shouldn’t be happy.”

“As you know, President Obama fired him, and essentially so did I,” the president said, referring to the fact that Mattis served as commander of the military’s Central Command under Obama, but retired a few months earlier than expected in 2013 after repeatedly clashing with Obama’s national security team over policy in the region, especially regarding Iran.

Trump then praised himself for providing money for soldiers in Afghanistan, and said that Mattis was “thrilled” when it happened.

He also said that he thought he himself “would’ve been a good general,” adding, “but who knows.”