More than a year after leaving his job as White House Chief of Staff, retired Marine Corps Gen. John Kelly has decided to air his opinions about his old boss, President Donald Trump.

During a Q&A session at Drew University in New Jersey, The Atlantic reported, Kelly opened up about a number of topics he'd previously held his tongue on, including the controversy surrounding Army Lt. Col. Alexander Vindman, who has been heavily criticized by the president and his supporters for testifying last fall during House impeachment hearings.

“He did exactly what we teach them to do from cradle to grave,” Kelly said of Vindman, per The Atlantic. “He went and told his boss what he just heard.”

Kelly went on to explain that U.S. policy, up until Trump's July 25 phone call with Ukrainian President Volodymyr Zelensky, was to militarily support Ukraine in its defense against Russia's military. “And so, when the president said that continued support would be based on X, that essentially changed. And that's what [Vindman] was most interested in.”

Kelly added: “We teach them, 'Don't follow an illegal order. And if you're ever given one, you'll raise it to whoever gives it to you that this is an illegal order, and then tell your boss.'

Trump doesn't exactly see it that way. Last week, Vindman and his brother were dismissed from their White House jobs and reassigned to the Department of the Army hours after Trump told reporters that he was “not happy” with Vindman.

Many pointed out that it is Trump's right to have who he wants working in the White House, but the removal raised more concerns about possible retaliation against Vindman for his role in the House impeachment inquiry.

The next day, Trump went after Vindman on Twitter, calling him “very insubordinate” and stating that he “was given a horrendous report by his superior….who publicly stated that Vindman had problems with judgement, adhering to the chain of command and leaking information.”

On Tuesday, the Trump stated in the Oval Office that while it was “up to the military” to decide on disciplinary action against Vindman, he imagined they would “certainly…take a look at that.”

There's no indication that's happening. Both ABC News and the Daily Beast, citing U.S. officials, report that he is not under investigation by the Army.

And while the Army has not made any public comments specifically mentioning an investigation or the lack thereof, the service has repeatedly backed Vindman in previous statements, saying he “served this country honorably” and has a “long history of selfless service.”

“Lt. Col. Vindman is afforded all protections anyone would be provided while performing his duties,” an Army spokesperson told Task & Purpose last week.

Kelly's comments drew critical tweets from Trump on Thursday, who said his former chief of staff had been “way over his head,” and that the job “just wasn't for him.”

“He came in with a bang, went out with a whimper,” Trump tweeted. “But like so many X's, he misses the action & just can't keep his mouth shut.”

Kelly isn't the only retired general deciding to go public with their support of Vindman — Gen. Joseph Dunford, former Chairman of the Joint Chiefs of Staff, told CNN's Barbara Starr in October that he came into regular contact with Vindman while he was on the joint staff.

Dunford called him “a professional, competent, patriotic, and loyal officer. He has made an extraordinary contribution to the security of our Nation in both peacetime & combat.”