President Donald Trump called former Defense Secretary Jim Mattis “the world’s most overrated general” during a tense White House meeting Wednesday with lawmakers over the growing Syria/Turkey conflict, according to sources familiar with the meeting.

The incident wasn’t the first time Trump has attacked the popular former Marine Corps general, once one of his most highly praised Cabinet officials. But since Mattis announced his resignation from the top Defense Department job last December, the president’s view of Mattis has increasingly soured.

The latest incident came after Senate Minority Leader Chuck Schumer, D-N.Y., invoked Mattis during the White House meeting, saying that Trump’s decision to withdraw U.S. forces from northern Syria could help the Islamic State group resurface.

Schumer quoted Mattis, who earlier this week said that “if we don't keep the pressure on, then ISIS will resurge. It's absolutely a given that they will come back.”

According to sources close to the meeting, Trump immediately cut off Schumer to attack Mattis. In an appearance on MSNBC Thursday morning, Schumer said he was shocked by the response.

“(The president) bragged that he was much better at this than Mattis,” he said. “Mattis is one of the most respected people here in Washington, by all parties. I worked with him closely.

“For the president to berate a man who has served the country, who is respected as a human being and as a general and as a Secretary of Defense, and not have a policy … what bothered Mattis was the same thing I think that bothers so many of us.”

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Mattis, in his resignation letter from the defense secretary post, said that his policy views no longer aligned with Trump’s, in particular when it came to support for American allies overseas.

Administration officials said Trump’s promises to quickly withdraw U.S. forces from the Middle East and Afghanistan also played a factor in Mattis’ decision to step down.

According to sources close to the meeting, Trump blasted Mattis as “not tough enough,” adding “I captured ISIS. Mattis said it would take two years. I captured them in one month.”

During his appearance on “Meet the Press” earlier this week, Mattis indicated he does not believe administration statements that ISIS is completely defeated.

"We have got to keep the pressure on ISIS so they don't recover," he said. “We may want a war over; we may even declare it over. You can pull your troops out — as President Obama learned the hard way out of Iraq — but the enemy gets the vote.”

Trump said earlier on Wednesday downplayed the U.S. withdrawal in Syria, saying that only about 28 U.S. troops were moved from forward bases in Syria in advance of planned Turkish military activities to keep them from getting caught up in a regional conflict.

But numerous Democratic and Republican lawmakers have criticized the move as abandoning Kurdish allies in the region and undermining U.S. military relationships worldwide.

The White House meeting was marked by several tense exchanges between the president and Democratic leaders, who are currently involved in impeachment investigations against the president over his alleged moves to push foreign allies to investigate the family of former Vice President Joe Biden, a rival candidate in the 2020 presidential race.

House Speaker Nancy Pelosi, D-Calif., said at one point Trump called her “a third-grade politician” and “a very sick person.” Pelosi in turn questioned Trump’s mental health.

On Thursday, ahead of a congressional briefing on the Syria situation, Sen. Tim Kaine, D-Va., called the president’s attack on Mattis “delusional” and praised the former U.S. Central Command leader as “one of the finest public servants I have ever worked with in 25 years of public life.”

Mattis remains one of the most popular figures in recent military history, both in the civilian world and within the ranks. A September 2018 Military Times poll found that nearly 84 percent of troops had a favorable view of his work leading the armed forces. Among officers, the figure was almost 90 percent.

When Mattis announced his resignation in December, he planned to serve another two months as defense secretary to ensure a smooth transition to a new Pentagon leader. But Trump abruptly fired him a few days later, leaving the defense secretary post vacant for almost seven months.

Trump also on several occasions has said that Mattis was “not too good” at his job. In his book released earlier this summer, Mattis declined to take any direct shots back at the president.

Mattis has not publicly commented on the latest round of attacks from Trump. Schumer said on Thursday he was offended on his behalf.

“Mattis wouldn't care what the president said about him, but he'd care that this country is off track,” he said.

Reporter Joe Gould contributed to this report.