In an open letter stressing core principles that have so far kept America from descending down a path toward military dictatorship, a bipartisan group of former Pentagon leaders is warning about what they say is an “exceptionally challenging civil military environment.”

Published Tuesday on the War On the Rocks website, the letter from eight former secretaries of defense and five former chairmen of the Joints Chiefs of Staff said geopolitical headwinds, lingering tensions from the Covid pandemic, and growing polarization of the American body politic have created an environment that necessitates a reminder of the constitutional foundations of civil-military relations and responsibilities.

“Politically, military professionals confront an extremely adverse environment characterized by the divisiveness of affective polarization that culminated in the first election in over a century when the peaceful transfer of political power was disrupted and in doubt,” the letter states. “Looking ahead, all of these factors could well get worse before they get better.”

The letter was published less than a week after President Biden came under intense criticism for using two Marines as backdrops during a Philadelphia speech that lambasted many Republicans as extremist threats to American democracy. Only days later, a Republican Army Reservist running for lieutenant governor of Arizona posted a photo of himself on social media in uniform and brandishing a handgun.

Retired military leaders have also gone on record in recent weeks suggesting that Mr. Biden and his deputies ignored the advice of military officers by pulling out of Afghanistan hastily, allowing that country to be rolled up by Taliban insurgents almost overnight.  

Mr. Biden’s predecessor, President Trump, also came under fire repeatedly for his attempts to get the military to do bidding outside the scope of constitutional norms, such as tamping down social unrest during the racial violence following the murder of George Floyd in the summer of 2020 or staging elaborate Independence Day parades on the National Mall in Washington.

Calling civilian control of the military “part of the bedrock foundation of American Democracy” that must be defended, the letter’s authors said that military officers owe their allegiance to the Constitution, and not one particular person or office. All three branches of the U.S. government have clearly delineated lines of authority over the military that must be upheld, they said.

“Ultimately, civilian control is wielded by the will of the American people as expressed through elections,” the letter said.

Military officials, even if they disagree with the orders of civilian leaders, must follow them “provided that the directives are legal,” the authors state, using italics for emphasis. Elected officials have a right to be wrong, they said, “even if other voices warn in advance that the proposed action is a mistake,” but it is on political leaders to “take responsibility for the consequences of the actions they direct.”

The group said the military must remain nonpartisan and accept that its members may not enjoy the same constitutional rights as other Americans in this regard. They also stressed that military officials can and should play only limited roles in law enforcement, and that they must accept the will of the voters who ultimately are supposed to wield power in a democracy.

“Because the voters (not the military) decide who will be commander-in-chief, they must prepare for whomever the voters pick — whether a reelected incumbent or someone new,” the letter said.

Signatories of the letter include secretaries of defense going back to the Clinton administration — William Cohen and William Perry — and Robert Gates, who served under the administrations of both George W. Bush and Barack Obama. Other Obama-era secretaries who signed on include Ashton Carter, Charles Hagel, and Leon Panetta. Two of Mr. Trump’s defense secretaries, Mark Esper and James Mattis, also signed the letter.

The Joint Chiefs commanders who signed the letter include Generals Martin Dempsey, who served during the Obama administration, and Joseph Dunford, who served during both the Obama and Trump administrations. Admiral Michael Mullen, also an Obama-era alumnus, and two generals from the administration of George W. Bush — Richard Myers and Peter Pace — attached their names to the letter.