Early June saw one of the most remarkable periods in US civil-military relations in decades. Donald Trump threatenedto deploy regular, active-duty troops to confront American citizens protesting racial injustice in cities across the country. The civilian and military leadership of the US Department of Defense balked at the possibility of sending troops to the street. Several retired officers spoke out against the proposition and in some cases, about Trump himself. For some watching, it looked like the American military had turned against the president.

While striking, the clash over using the military to quell protests was just the most acute incident in a long string of tensions between Trump and the US military — and things may well get worse with the upcoming November presidential election.

The US military maintains a nonpartisan stance in domestic politics, which is supported by the US Constitution, law, Department of Defense regulation and norms to which officers are socialised from early in their careers. Far more than any contemporary president, Trump has violated this nonpartisan ethic.

Trump has treated the military as a political ally, seeking to use its resources for partisan advantage and its members as political props. He has made explicitly partisan comments to military audiences and intervened in military justice to pardon or restore the rank of military personnel accused of war crimes and then invited the men to attend campaign events. His staff ordered that the Naval vessel named after one of his political rivals, the USS John McCain, be blocked from view on the president’s May 2019 visit to Yokosuka Naval Base in Japan. He signed a controversial ‘Muslim ban’ on immigration in the Pentagon’s Hall of Heroes with military personnel assembled in the audience.

Trump criticised by retired military leaders

Observers of civil-military relations were alarmed by these and other incidents — but, by far, the most disturbing has been Trump’s early June threat to send military forces to confront protesters. Some early protests had involved property destruction and looting and several governors activated the National Guard to assist in stabilising the situation. The National Guard is a militia that normally is controlled by state governors, although it can be federalised allowing the president to control it directly.

But, by 1 June Trump was reportedly ready to send 10,000 regular military troops to the streets — forces usually used in external conflicts. He did this despite the fact that no governors had requested the troops. Trump nevertheless threatened to invoke the Insurrection Act which would have allowed him to deploy the troops without the governors’ permission. Forces were brought to the Washington DC area, including some from the combat-ready 82nd Airborne Division. In a call with Defense Secretary Mark Esper and the nation’s governors, Trump warned governors to ‘dominate the streets,’ while one of his allies, Sen. Tom Cotton, urged the president in controversial op-ed to ‘send in the troops.’

For decades, the American military has remained enormously popular with the public, even while its confidence in other US institutions has declined.

The move was viewed by many as an attempt to use the military for partisan advantage — to enforce Trump’s claim that he would restore ‘law and order’ — a phrase that historically has had strong racial overtones in the United States. When Esper and Chairman of the Joints Chief of Staff, Gen. Mark Milley accompanied Trump in a walk through a park in front of the White House it added to the perception that the military was siding with Trump. Federal agents moments before had used pepper spray and other non-lethal methods to disperse peaceful protesters so that Trump could take a photo with a bible in front of an adjacent church. Gen. Milley subsequently apologised for his role in the affair.

The event opened a veritable floodgate of criticism from retired military leaders. Former Secretary of Defense and Marine general, Jim Mattis decried Trump’s actions and criticised him for dividing the country. Two former chairmen of the Joint Chiefs of Staff, Adm. Michael Mullen and Gen. Martin Dempsey, spoke out. Other national security professionals, including several former secretaries of defense, also criticised the possible use of the military to repress American citizens exercising their First Amendment rights. Subsequently, Esper stated that he did not support invoking the Insurrection Act. Trump retreated and the active-duty troops sent to the DC area were sent home.

What is to come in November

To be sure, this is not the first time that retired military officers have spoken out. In 2006 several criticised then Secretary of Defense Donald Rumsfeld for his management of the US war in Iraq. Many of them also regularly endorsecandidatesduring elections. Still, the number and stridency of the comments was remarkable.

Some observers welcomed the interventions by these prominent military leaders, viewing it as an important reiteration of the military’s commitment to uphold the Constitution and embrace democratic norms. Others saw it as an essential corrective to Trump’s efforts to portray the military as his partisan ally and draw it into the center of domestic politics. In this view, there were political consequences to staying silent and it was therefore important for retired officers to push-back on Trump’s plans.

Others, even some sympathetic to the generals’ message, worried about the precedent it set for the future. Retired military leaders were making statements that had clear partisan implications — in some cases, explicitly so. While they are private citizens, Americans do not always distinguish retired from currently serving officers. By all appearances, a portion of the military was criticising a sitting president.

Regardless, the degree of retired officer dissent — and the attention it garnered — signified something deeply unhealthy about American democracy. For decades, the American military has remained enormously popular with the public, even while its confidence in other US institutions has declined. Few paid much heed to the civilian national security professionals who spoke out. It was left to the generals to help adjudicate the democratic process.

For the moment, the tensions have passed. The troops have been sent home and there is no talk of sending them to the streets. Protests have remained overwhelmingly peaceful. Yet, the events of June may be just a preview of what is to come in November. In the event Donald Trump contests the presidential election, or foreign actors engage in serious mischief in the electoral process on his behalf, protests are inevitable. What happens then is hard to foresee. One thing that is certain, however — it is likely to put new strain on the civil-military relationship.