What are the chances that Donald Trump’s presidency could be brought to a halt by a military uprising? At first glance, it seems like a strange question, and the idea of a military coup in a developed and seemingly stable Western democracy feels far-fetched. But then again, memories are short: in May 1958, France faced a military revolt in Algeria that threatened to spread to the French mainland. Without it, General Charles de Gaulle would never have been president, and the Fifth Republic would never have been born.

It may not be necessary to start preparing for military takeover in the US, but with American politics at their most unpredictable for years, the possibility of such a course of action has been mooted in the US mainstream since before Trump was even elected. As his presidency progresses, academics, bloggers and columnists are still mooting the idea.

So if we take it up as a thought experiment, what stands in the way of an American coup actually happening? Plenty. First and foremost is the ingrained legitimacy of the civilian commander-in-chief, to whom the US military has been subordinate for 250 years. But it’s important to remember that the US military’s oath is taken to defend the Constitution. If there were ever clear evidence that the president had acted to subvert the Constitution, and Congress proved unable or unwilling to impeach that president, the military’s first obligation might come into question.

The second major obstacle to a successful coup is the fact that military authority is not invested in one person; the National Guard, unless called into federal service, is subject to the authority of state governors. Meanwhile, the US’s gun control laws mean that any potential leaders of a military coup would have to deal with the problem of a well-armed citizenry.

To neutralise these two fronts of potential resistance, the plotters of an American military coup would need to deny them information on what’s happening, and just as importantly to deny any would-be loyalists the time or ability to act.

The last major obstacles are the sheer size of the US and the way power is diffused across it. Any coup would have to do more than simply secure Washington, DC; to seize maximum control over the centres of political, financial and media power, it would also (at a minimum) need to secure Manhattan and large parts of Los Angeles. This in turn would mean deploying troops from the 10th Mountain Division at Fort Drum, New York, the 1st Marine Division at Camp Pendleton in San Diego, and the Marine base at Quantico, Virginia.

However, any plot would have two crucial things working in its favour. First, the sheer implausibility of a coup means that the US domestic intelligence agencies, particularly the FBI, aren’t looking for signs of unrest within the military. And second, the sheer size and complexity of the US military means that a conspiracy involving those of sufficiently high rank could move substantial military assets without raising too many questions.

Locked down

The most critical thing any successful plot would have to do is to shut down all communications across the continental US. One of the key reasons why the 2016 coup attempt in Turkey failed was that the president was able to put out a counter-narrative to the coup plotters via FaceTime, and was therefore able to mobilise civilian demonstrations against the military in very large numbers in a very short space of time. Given Trump’s fondness for Twitter, we can easily see him doing something similar.

But a nationwide communications blackout might be easier to achieve than it sounds. Several reports, both private and governmental, have pointed out major weaknesses in the US power and utility grids, which were designed in an era before computers were routinely networked. This makes them extremely vulnerable to cyberattack.

The US makes no secret of having an offensive cyber capability of its own; indeed, US Cyber Command has stated that it has tried to use this technology against the so-called Islamic State (albeit with little success). Such a cyberattack could be staged to look like it came from a foreign enemy, and the narrative of a foreign attack could then provide the pretext for deploying troops on the streets.

Any successful plot would also need to secure the military’s own communications network, which would mean taking the National Military Command Center at the Pentagon, through which any order to the US’s nuclear arsenal or conventional military must pass.

Located at the heart of the Pentagon, this system operates continuously, and its most sensitive parts are manned by small crews; for the system to be not just taken but maintained, those people would need to be supporters of the coup, or at least compliant with it. If the leader of the coup was someone with military legitimacy – the secretary of defence, say, or the chairman of the joint chiefs of staff – it would not be impossible to arrange this.

Any successful coup would also need to physically secure the president. Unlike some of his predecessors, Trump actually makes this relatively straightforward: his Mar-a-Lago retreat in Florida is on a peninsula, making it very easy to cut off from the mainland. All the plotters would have to do is create a roadblock and secure a helipad.

This in turn means the ideal time to mount a coup would be over a public holiday. Not only would Trump would almost certainly be ensconced in his Florida getaway, but most ordinary people would be away from their homes and government departments would be minimally staffed.

This article is just a sketch, and has obviously left out a great deal of the detailed planning that would actually be required for a real-life coup to happen. How would the coup leaders deal with Congress? How would any armed resistance be dealt with? Still, the point is clear: a successful military coup in the US is extremely unlikely, but under the right circumstances, it’d be far from impossible to achieve.