Former US Defense Secretary Jim Mattis speaks during a meeting with Israeli Defense Minister Avigdor Lieberman (not in the picture) at the Pentagon in Washington DC, the United States, on Oct. 19, 2017. (Xinhua/Yin Bogu)

 
Former US Defense Secretary Jim Mattis broke silence on Wednesday amid the ongoing turbulent unrest across the United States, saying that President Donald Trump "tries to divide" the American people.

"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," said the revered Marine general, who resigned as the Pentagon chief in December 2018 in protest against Trump's Syria policy.

"We are witnessing the consequences of three years of this deliberate effort. We are witnessing the consequences of three years without mature leadership," Mattis continued in an article carried by the Atlantic magazine.

"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; to past generations that bled to defend our promise; and to our children," he said.

Mattis's excoriation came as Trump threatened to send in active-duty military forces to quell the ongoing protests against police brutality and racial discrimination that have spread to over 300 US cities and towns following the killing of George Floyd, an unarmed black man in Minneapolis, by white police.

"We should use our military only when requested to do so, on very rare occasions, by state governors. Militarizing our response, as we witnessed in Washington, D.C., sets up a conflict -- a false conflict -- between the military and civilian society," Mattis said.

Noting that the protesters were "rightly demanding" equal justice under law, Mattis said he has "watched this week's unfolding events, angry and appalled."

"It is a wholesome and unifying demand -- one that all of us should be able to get behind. We must not be distracted by a small number of lawbreakers," he continued. "The protests are defined by tens of thousands of people of conscience who are insisting that we live up to our values -- our values as people and our values as a nation."

"We must reject and hold accountable those in office who would make a mockery of our Constitution," said the former defense secretary.

Mattis also bluntly berated Trump's posing for a photo op in front of a fire-damaged church near the White House. The president, flanked by senior administration officials including Defense Secretary Mark Esper and Chairman of the Joint Chiefs of Staff Mark Milley, visited on Monday the St. John's Church minutes after police used non-lethal weapons to disperse peaceful protesters nearby.

"When I joined the military, some 50 years ago, I swore an oath to support and defend the Constitution," Mattis wrote. "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."

Apparently outraged by Mattis's remarks, Trump took to Twitter to fight back, saying he "had the honor of firing Jim Mattis, the world's most overrated General."

"His primary strength was not military, but rather personal public relations," Trump said. "I didn't like his 'leadership' style or much else about him, and many others agree. Glad he is gone!"

On May 25, 46-year-old Floyd died after a white police officer knelt on his neck for almost nine minutes until he stopped breathing.

In a video posted online, the victim is heard saying "I can't breathe," while three other police officers stand close by.

Referring to the death of Floyd and the ensuing nationwide unrest, former President Barack Obama -- himself an African American -- said Wednesday that "as tragic as these past few weeks have been, as difficult and scary and uncertain as they've been, they've also been an incredible opportunity for people to be awakened to some of these underlying trends."