Trump put the issue out in front Monday in a made-for-TV show of force.

After having police fire tear gas to clear away peaceful protestors in front of the White House, he walked with Defense Secretary Mark Esper and Joint Chiefs Chairman General Mark Milley at his side to a nearby church to pose for pictures.

Minutes earlier, he had declared that he was dispatching "thousands and thousands of heavily armed soldiers" to help quell unrest, which appeared to invoke the rarely used Insurrection Act to involve the US Army in domestic peace-keeping.

The Pentagon stressed that the Insurrection Act had not been activated.

But Trump's words, and the picture of Milley in his camouflage battle dress at the White House, left many nervous.

Likewise did Esper telling governors of US states earlier Monday that they should "dominate the battlespace" to end the protests, sounding like he too viewed the situation as war.

One week after the killing of handcuffed African American George Floyd by a Minneapolis policeman sparked protests and riots for racial justice across the country, such talk sparked anger and concerns that Trump would use the military against political foes, and to boost his own stature.

"America is not a battleground. Our fellow citizens are not the enemy," said retired General Martin Dempsey, who held Milley's job from 2011 to 2105.

"I am not convinced that the conditions on our streets, as bad as they are, have risen to the level that justifies a heavy reliance on military troops," Mike Mullen, Dempsey's predecessor as the top Pentagon commander, wrote in the Atlantic on Tuesday.

"Furthermore, I am deeply worried that as they execute their orders, the members of our military will be co-opted for political purposes."

- 'Not aware' -

The Pentagon sought Tuesday to dampen the concerns, even as hundreds of army policemen were placed on standby for duty if violence continued in the US capital.

A senior official, speaking on grounds of anonymity, insisted that Esper's "battlespace" was simply his habit of using the jargon of the US military.

"It's the common term we use for the area we are operating in," he said.

As for Milley's and Esper's presence when Trump made his political display, the official claimed they had been called to the White House at short notice -- hence Milley's camouflage uniform -- and did not know it was going to happen.

"The president indicated an interest in viewing the troops outside and the secretary and the chairman went with him," the official said.

"They were not aware that the police and law enforcement had made a decision to clear the square."

- 'Autocratic rule' -

That failed to douse concerns that the two top military leaders were being sucked and pressured into Trump's political plans.

"I remain gravely concerned about the President Trump's seemingly autocratic rule and how it affects the judgement of our military leadership," said the chair of the House Armed Services Committee, Adam Smith.

"The role of the US military in domestic US law enforcement is limited by law," he added.

"It must not be used in violation of those limits and I see little evidence that President Trump understands this fundamental premise."

Joe Biden, the Democratic candidate for president, accused Trump of "using the American military against the American people."

It was clear, too, that African Americans in the US military had their focus on brutality toward blacks and less so on Trump's machinations.

"Just like most of the Black Airmen and so many others in our ranks ... I am outraged at watching another Black man die on television before our very eyes," tweeted Chief Master Sergeant Kaleth Wright, the senior-most enlisted man in the US Air Force.

"I am George Floyd," he wrote.