June 4 (UPI) -- Former U.S. Defense Secretary Jim Mattis, who left his post more than a year ago over a disagreement with President Donald Trump on Syria, has roundly criticized his former boss amid national backlash spurred by the police killing of George Floyd.
In an essay published in The Atlantic, Mattis accuses Trump of being divisive and denounces him for his response to protests nationwide.
"The words 'Equal Justice Under Law' are carved in the pediment of the United States Supreme Court. This is precisely what protesters are rightly demanding," he wrote. "We must not be distracted by a small number of lawbreakers. 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.
Trump has repeated this week that he plans to send active U.S. military forces into cities to suppress violent demonstrations if local leaders can't bring them under control -- a threat that has been criticized by some state leaders and rejected outright by others.
"Militarizing our response, as we witnessed in Washington, D.C., sets up a conflict -- a false conflict -- between the military and civilian society," Mattis wrote. "It erodes the moral ground that ensures a trusted bond between men and women in uniform and the society they are sworn to protect, and of which they themselves are a part."
In his essay, he urges citizens to "reject and hold accountable" elected leaders who "make a mockery of our Constitution."
"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," he added, saying the entire situation has made him "angry and appalled."
"We are witnessing the consequences of three years of this deliberate effort. We are witnessing the consequences of three years without mature leadership."
Trump slammed Mattis for the essay late Wednesday.
"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," he tweeted.
"His primary strength was not military, but rather personal public relations. 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."
Defense Secretary Mike Esper mildly broke ranks with Trump on Wednesday by saying the situation has not yet reached a point that requires military intervention.
Trump's pledge to send military forces does have some support among Republican lawmakers.
Arkansas Sen. Tom Cotton, writing in The New York Times, criticized the response by some local officials as "feckless" and said it's "past time to support local law enforcement with federal authority."
U.S. Attorney General William Barr beefed up security to address protesters this week in Washington, D.C., which has included deploying military vehicles and federal law enforcement agents in tactical attire bearing no identifiable insignia.
Barr is said to have ordered forces to clear away demonstrators near the White House on Tuesday so that Trump could walk to a nearby church to pose for photos while holding a Bible. Those security tactics have been widely criticized and Pentagon adviser James Miller resigned on Wednesday in protest.
A U.S. Marine Corps general, Mattis resigned as Trump's Pentagon chief in December 2018 after disagreements over Trump's handling of Turkish military operations and support in Syria.