There are at least 2 situations that I'm aware of:

*1* For July 4, 2018, Trump wanted a North Korea style parade "in his honor". Some news articles call it a French Bastille-day type of parade [0] because his discussions of what kind of parade he wanted started after returning from the 2017 Bastille Day celebrations (July 17).

> But the gulf between Trump and the generals was not really about money or practicalities, just as their endless policy battles were not only about clashing views on whether to withdraw from Afghanistan or how to combat the nuclear threat posed by North Korea and Iran. The divide was also a matter of values, of how they viewed the United States itself. That was never clearer than when Trump told his new chief of staff, John Kelly—like Mattis, a retired Marine Corps general—about his vision for Independence Day. “Look, I don’t want any wounded guys in the parade,” Trump said. “This doesn’t look good for me.” He explained with distaste that at the Bastille Day parade there had been several formations of injured veterans, including wheelchair-bound soldiers who had lost limbs in battle.

> Kelly could not believe what he was hearing. “Those are the heroes,” he told Trump. “In our society, there’s only one group of people who are more heroic than they are—and they are buried over in Arlington.” Kelly did not mention that his own son Robert, a lieutenant killed in action in Afghanistan, was among the dead interred there.

> “I don’t want them,” Trump repeated. “It doesn’t look good for me.”

> The subject came up again during an Oval Office briefing that included Trump, Kelly, and Paul Selva, an Air Force general and the vice-chairman of the Joint Chiefs of Staff. Kelly joked in his deadpan way about the parade. “Well, you know, General Selva is going to be in charge of organizing the Fourth of July parade,” he told the President. Trump did not understand that Kelly was being sarcastic. “So, what do you think of the parade?” Trump asked Selva. Instead of telling Trump what he wanted to hear, Selva was forthright.*

> “I didn’t grow up in the United States, I actually grew up in Portugal,” Selva said. “Portugal was a dictatorship—and parades were about showing the people who had the guns. And in this country, we don’t do that.” He added, “It’s not who we are.”

> Even after this impassioned speech, Trump still did not get it.

> It turned out that the generals had rules, standards, and expertise, not blind loyalty. The President’s loud complaint to John Kelly one day was typical: “You fucking generals, why can’t you be like the German generals?”

> “Which generals?” Kelly asked.

> “The German generals in World War II,” Trump responded.

> “You do know that they tried to kill Hitler three times and almost pulled it off?” Kelly said.

> But, of course, Trump did not know that. “No, no, no, they were totally loyal to him,” the President replied. In his version of history, the generals of the Third Reich had been completely subservient to Hitler; this was the model he wanted for his military. Kelly told Trump that there were no such American generals, but the President was determined to test the proposition.

Some of the generals mentioned in the New Yorker article have signed the statement.

*2* After Trump's attempted insurrection on Jan 6, 2021, many people were convinced that Trump would start a nuclear war because he was angry and was going to throw a temper-tantrum: Congress did not overturn the 2020 election, and no one hanged Pence. So some of the generals agreed that if he decided to "push the button" then they were not going to process the orders [1].

> In the aftermath of the Jan. 6 attack on the U.S. Capitol, Joint Chiefs of Staff Chairman Gen. Mark Milley — then former President Donald Trump's top military adviser — took precautions to limit Trump's ability to launch a military strike or deploy nuclear weapons, according to a new book by Bob Woodward and Robert Costa of The Washington Post.

> In "Peril," Woodward and Costa write that Milley was afraid Trump had constructed "his own alternate reality about endless election conspiracies" and was worried the former president could "go rogue," CNN reported.

> In an rare move, the outlet reported, Milley called a secret meeting of senior military officials at the Pentagon on Jan. 8 to review the process for military action — including launching nuclear weapons. He instructed those in charge of the National Military Command Center, the Pentagon's war room, not to take orders from anyone without his involvement.

> Milley also reassured Chinese Gen. Li Zuocheng of the People’s Liberation Army that the U.S. had no intention of launching a strike against China, according to the paper. It was one of two secret phone calls shared with Li on the issue.

Holy cow! Calling his counterpart in China promising not to launch nukes if Trump went off the rails? [2]

[0] - https://www.newyorker.com/magazine/2022/08/15/inside-the-war...

[1] - https://www.bbc.com/news/world-us-canada-42065714

[2] - https://www.usatoday.com/story/news/politics/2021/09/14/gen-...