President Trump responded to criticism from former Defense Secretary James Mattis by calling him an “overrated” military leader whom he relished firing.

“Probably the only thing Barack Obama and I have in common is that we both had the honor of firing Jim Mattis, the world’s most overrated General,” Mr. Trump tweeted. “I asked for his letter of resignation, & felt great about.”

Mr. Mattis, a retired four-star Marine general whom the president previously called a hero, criticized the president Wednesday for “militarizing” the federal response to nationwide protests over police brutality. He called Mr. Trump “the first president in my lifetime who does not try to unite the American people — does not even pretend to try.”

He served two years as Defense secretary before leaving in January 2019.

The president said of Mr. Mattis, “His nickname was ‘Chaos’, which I didn’t like, & changed it to ‘Mad Dog’. His primary strength was not military, but rather personal public relations.”

In fact, Mr. Mattis was given the nickname “Mad Dog” in the military long before Mr. Trump was elected. A San Diego Tribune article in 2013 refers to the nickname, noting that Mr. Mattis didn’t like the moniker.

Said the president, “I gave him a new life, things to do, and battles to win, but he seldom ‘brought home the bacon’. I didn’t like his ‘leadership’ style or much else about him, and many others agree. Glad he is gone!”

Mr. Mattis wasn’t fired; he resigned after clashing with the president over the administration’s policy in Syria.