A person holds a "Black Lives Matter" sign as as a heavy cloud of tear gas and smoke rises after being deployed by Seattle police as protesters rally against police brutality and the death in Minneapolis police custody of George Floyd, in Seattle, Washington, U.S. June 1, 2020. REUTERS/Lindsey Wasson
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Editor’s Note: Peter Bergen is CNN’s national security analyst, a vice president at New America, and a professor of practice at Arizona State University. His new book is “Trump and His Generals: The Cost of Chaos.” The opinions expressed in this commentary are his own. View more opinion at CNN.

CNN —  

Not since one of President Donald Trump’s heroes, Gen. Douglas MacArthur, led a mounted charge in 1932 to disperse an encampment of homeless veterans just outside the White House has the country seen such an application of violence against unarmed protesters outside “the People’s House.” On Monday evening police, with National Guard troops in reserve, attacked peaceful protesters gathered outside the White House with rubber bullets and tear gas. It’s the kind of scene we associate with dictatorships, not western democracies.

Even worse was the purpose of this travesty – which was to allow President Trump a photo op outside St. John’s, the “church of the presidents” just outside the White House grounds.

There Trump held up a bible for the cameras, which will surely be an iconic image of his presidency as the coronavirus ravages the United States and riots and protests rage in its cities.

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Just as bad as the attacks on the peaceful protesters outside the White House were Trump’s threats Monday to send the federal military to quell unrest in American cities, which is simply not their job. What makes it particularly odd is that Trump frequently complains that US troops in Afghanistan are acting as a “police force.” Like so much of what Trump says that isn’t true, but even the President realizes on occasion that the federal US military doesn’t perform a law enforcement function for good reason; it’s not what it is trained to do. Also, the Pentagon simply can’t go to war with its own citizens.

Indeed it is barred from doing so by the Posse Comitatus Act of 1878, although under some very rare circumstances, federal troops have been deployed in the US. The last time they were called up for such duty was almost three decades ago during the 1992 Los Angeles riots which followed the acquittal of police officers who brutally beat Rodney King. More than 50 people were killed in the riots. The federal troops were called in at the invitation of California’s governor and they were not unilaterally deployed as President Trump has threatened to do.

Trump’s discussion of the sometimes violent protests that have occurred across the United States over the past week with US governors on a phone call Monday that became public in a leaked audio confirms that he and his “war cabinet” have a militarized view of the unrest in American cities.

Trump said that he had put US Joint Chiefs Chairman Army Gen. Mark Milley “in charge,” which is a strange formulation since the United States’ top military officer is not supposed to be responsible for domestic law enforcement. That’s the role of the police and in some cases, the National Guard under the control of each states’ governor.

On Monday’s call with the governors, US Defense Secretary Mark Esper blathered about dominating “the battle space” as if the protests and riots in American cities were taking place in Baghdad in 2003.

Gen. Tony Thomas, who ran US Special Operations Command and also US Joint Special Operations Command – the unit that killed Osama bin Laden – tweeted to his relatively small group of some 1,300 followers on Monday night: “The “battle space” of America??? Not what America needs to hear…ever, unless we are invaded by an adversary or experience a constitutional failure…ie a Civil War…”

Good for Thomas, but his tweet has received scant attention as yet. We need more senior retired generals to say that violence against peaceful protesters is unacceptable and that using the US military aside from the national guard to police protests is fundamentally an un-American idea.

A retired top military officer who also just stepped up the plate is former US Joint Chiefs Chairman Admiral Mike Mullen, who wrote in The Atlantic Tuesday evening: “It sickened me yesterday to see security personnel—including members of the National Guard—forcibly and violently clear a path through Lafayette Square to accommodate the president’s visit outside St. John’s Church. I have to date been reticent to speak out on issues surrounding President Trump’s leadership, but we are at an inflection point, and the events of the past few weeks have made it impossible to remain silent.”

Adm. Bill McRaven, the architect of the bin Laden raid, and Gen. Stanley McChrystal, who turned Joint Special Operations Command into one of the most lethal fighting forces in US history, have been willing to call out the President for his dishonesty and divisiveness.

But isn’t it time to hear now also from former US Defense Secretary Jim Mattis, a retired four-star general who commanded CENTCOM that oversees America’s wars in the greater Middle East and who led the US Marines into Baghdad in 2003?

Or from former national security adviser Lt. Gen. H.R. McMaster who fought heroically both in the first Gulf War and the Iraq War and whose PhD dissertation that became a book about the Vietnam War is one of the key texts about the proper role of relations between a US president and his generals?

It’s past time for Mattis to abandon his position that he won’t speak out against President Trump. In his 2019 autobiography “Call Sign Chaos,” Mattis observed, “I’m old fashioned: I don’t write about sitting Presidents.” This conception of the proper role of retired senior US generals that they shouldn’t make statements about contemporaneous political matters may work in times of normalcy but this is not one of those times.

During his 2019 book tour Mattis told Jeffrey Goldberg of The Atlantic that his duty of silence about Trump wasn’t “eternal.”

Now would be an important time for Mattis to break his silence. Mattis can use his considerable stature for the common good to push back on Trump’s dangerous ideas about deploying the US federal military in American cities and also to condemn the President’s role in attacking peaceful protestors outside the White House.

Retired four-star Marine Gen. John Kelly also has the experience and gravitas to make similar points. Kelly led SOUTHCOM which oversees all of US military operations south of the US-Mexico border and later became Trump’s chief of staff.

And McMaster could also use his considerable stature to speak out about the politicization of the US military by the Trump administration.

McMaster’s book described the failures of American generals to stand up to President Lyndon Johnson and to provide him truthful military advice about the conduct of the Vietnam War, which Johnson saw largely through the lens of his domestic political fortunes.

We have reached a similar point in the United States where the Pentagon is being used for Trump’s political purposes and it’s time to push back.

This column has been updated to include a reference to Admiral Mike Mullen’s new article in The Atlantic.