Spreading a proven lie and advocating a war-crime, even as innocents are dying, Donald Trump offers a terrifying insight into his own mental state, writes Donal O’Keeffe.

As news came in of the terrorist atrocity in Barcelona, President Trump took, predictably, to Twitter. He tends to be a lot quicker to the Tweet Machine when the fascists mowing down innocents aren’t the folks who voted for him.

“Study what General Pershing of the United States did to terrorists when caught,” Trump thundered. “There was no more Radical Islamic Terror for 35 years!”

Trump was alluding to claims that US General John J. Pershing supposedly executed dozens of Muslim prisoners in the Philippines in the early 1900s, a myth Trump has been spreading since at least February of 2016, when he addressed a rally in North Charleston, South Carolina.

Describing the story as “something you can read in the history books — not a lot of history books because they don’t like teaching this”, Trump praised General Pershing as a “rough guy, rough guy”, as he recounted his tale to a baying crowd.

“They were having terrorism problems, just like we do. And he caught 50 terrorists who did tremendous damage and killed many people. And he took the 50 terrorists, and he took 50 men and he dipped 50 bullets in pigs’ blood — you heard that, right?”

The mention of pigs’ blood is of course a reference to the notion that pigs are anathema to all Muslims.

“And he had his men load his rifles and he lined up the 50 people, and they shot 49 of those people. And the 50th person, he said, ‘You go back to your people and you tell them what happened.’ And for 25 years there wasn’t a problem.”

As the New York Daily News columnist Sol Stern noted, Trump two months later claimed that the period of peace brought about by this war crime was 42 years. And now, more than a year later, it was 35 years.

“Trump did get one thing right in his speech,” says Stern. “Historians don’t teach this story. It never happened!”

Someone who has, unlike Trump, actually studied what General Pershing did is Brian M. Linn, a professor of history at Texas A&M University. He is the author of “Guardians of Empire”, a study of the US military presence in Asia from 1902 to 1940.

“It’s a made-up story,” Professor Linn told the Washington Post. “It doesn’t seem to matter how many times people say this isn’t true.” Linn first encountered this story after September 11th, 2001, as the myth was spread by email in the wake of the terrorist attacks on the US.

“It seemed to me to be coming from sources that were strongly anti-Muslim,” Linn said, “not military historians or scholars.” One possible source of this myth may date to the 1939 film “The Real Glory”, wherein Gary Cooper plays a doctor in 1906 Manila. At one point, Cooper’s character threatens to bury Muslim rebels in pigskins.

Another possible source dates to the Indian Mutiny of 1857. It was rumored by Hindu soldiers that the grease on musket-cartridges was pig fat. As you had to tear open the cartridge with your teeth before loading, the Muslims would be ingesting pork. This is likely to be apocryphal too.

As to the detail about pigs, the fact-checking website Snopes notes, “the desire for simplistic solutions to complex problems has spawned several widely-circulated notions that seek to transform a fight against terrorism to the easily-manageable level of a horror film or a comic strip. One popular notion is the concept that a pig is to a Muslim as a crucifix is to a vampire: simply arm yourself with a porker, and you can use it to render even the most fanatical terrorist helpless, sending him cowering in fear lest he come into contact with anything porcine.”

This line of thought contains any number of erroneous assumptions, not least among them the notion that all Muslims are terrorists and that all Muslim terrorists are devout Muslims. It confuses the devout with the fanatical and it makes the fundamental mistake of imagining that Islam – a faith with 1.5 billion adherents – is a monolithic, homogenous unit, when of course it isn’t, and is instead made up of many different sects and sub-sects. Not unlike Christianity.

Still, it tells you everything you need to know about the mental state of the most powerful man in the world that – even as people are still dying in the midst of a terrorist atrocity – his first thought is to reference a made-up story – and one he knows to be made-up – and to suggest that repeating an absolutely horrific war crime is the best, immediate course of action.

“You don’t have to be a psychiatrist to see that Trump loves telling this story because of his own barely repressed bloodlust,” says Sol Stern. “The young man who dodged the draft, who never picked up a gun in defense of his country, now fantasizes about tough American soldiers solving problems by slaughtering America’s enemies by any means, fair or foul.”

That Trump could not actually condemn neo-Nazis last week without drawing a false equivalence to those protesting against them should serve as a warning to anyone who thinks that the departure from the White House of Steve Bannon – the far-right guru who helped Trump win the white nationalist vote – will mean a kinder, gentler Trump.

Trump built his political career on the racist lie that Barack Obama was not born in the United States and thus the first Black US president was illegitimately in the White House.

Trump knows full well that his story about General Pershing has been utterly debunked. He doesn’t care. The man who was elected at least in part by fake news stories has no compunctions about roaring that anything which disagrees with him is fake news. And he knows that his audience doesn’t actually care if he’s lying.

Once again, Donald Trump proves himself the living embodiment of HL Mencken’s observation: “The demagogue is one who preaches doctrines he knows to be untrue to men he knows to be idiots”.