James Mattis holds nothing back.

Courtesy of NBC News

“Donald Trump is the first president in my lifetime who does not try to unite the American people — does not even pretend to try. Instead, he tries to divide us,” Mattis wrote in a statement published by The Atlantic.

“Instructions given by the military departments to our troops before the Normandy invasion reminded soldiers that ‘The Nazi slogan for destroying us … was ‘Divide and Conquer.’ Our American answer is ‘In Union there is Strength.’ We must summon that unity to surmount this crisis — confident that we are better than our politics,” Mattis wrote.

In the stunning rebuke of his former boss, Mattis, a retired general, said he’d promised to defend the Constitution when he was sworn into the Marine Corps “some 50 years ago.”

“Never did I dream that troops taking that same oath would be ordered under any circumstance to violate the Constitutional rights of their fellow citizens — much less to provide a bizarre photo op for the elected commander-in-chief, with military leadership standing alongside,” Mattis wrote, referring to Monday night’s federal show of force to clear protesters from the front of the White House.

“We know that we are better than the abuse of executive authority that we witnessed in Lafayette Square. We must reject and hold accountable those in office who would make a mockery of our Constitution,” he wrote.

“We do not need to militarize our response to protests. We need to unite around a common purpose,” wrote Mattis, whom Trump would often refer to as “Mad Dog,” a nickname Mattis didn’t like.

Trump, he said, is a divider, and the country is “witnessing the consequences of three years of this deliberate effort.”

“We can unite without him, drawing on the strengths inherent in our civil society. This will not be easy, as the past few days have shown, but we owe it to our fellow citizens,” he wrote.

I think that Trump has finally crossed a line from which he cannot recover. 

Threatening to use federal troops against protesters in this country, was simply a bridge too far, and I imagine that there are a whole lot of Trump’s former supporters and associates who find themselves no longer able to support him. 

I don’t know that they will all write scathing op-eds like this one, but I know that they certainly should.