In a meeting on Wednesday that included Senate Minority Leader Chuck Schumer, House Majority Leader Steny Hoyer and House Speaker Nancy Pelosi, President Trump trash talked former Defense Secretary James Mattis, calling him "the world's most overrated general," per a Democratic source familiar with the meeting's events.

What we know: Lawmakers met to discuss the ongoing situation in northern Syria, where Turkish forces, emboldened by the withdrawal of U.S. troops, have invaded.

In Wednesday's White House meeting, Schumer attempted to read a quote from Mattis, stating: "if we don't keep the pressure on, then ISIS will resurge. It's absolutely a given that they will come back," according to a Democratic source.

But Trump reportedly cut Schumer off, asserting Mattis "wasn’t tough enough."

"I captured ISIS," Trump touted, adding, "Mattis said it would take 2 yrs. I captured them in 1 month."

Chairman of the Joint Chiefs of Staff Mark Milley clarified: "ISIS is defeated not destroyed."

Democrats said they walked out of the meeting — the first between Trump and Pelosi since the speaker launched a formal impeachment inquiry — after the president had a "meltdown."

Between the lines: Mattis exited the Trump administration in December, penning a letter to Trump in which he said that the president should "have a Secretary of Defense whose views are better aligned with [his]."

In the letter, Mattis also criticized America's fraying relationships with foreign allies, and its coziness with "countries whose strategic interests are increasingly in tension with ours," such as Russia and China.

Go deeper: Trump on Syria's Kurds: "They're not angels"