A COUPLE of days after the chemical weapons attack in Syria, some Twitter users in America began sharing a theory: the pictures had been concocted as a pretext for launching a missile attack. The notion was endorsed by Alex Jones, who runs a website called Infowars, which has successfully spread the idea that the Sandy Hook school shooting in Connecticut was a hoax and that Hillary Clinton was involved in a paedophile ring run from a pizzeria in Washington, DC. Mr Jones was until recently a fervent supporter of Donald Trump. Campaigning last year, candidate Trump returned the favour: “Your reputation is amazing, I will not let you down,” Mr Trump said. Now, it seems, he has.

The story of how Mr Jones fastened onto his Syria conspiracy has been pieced together by Ben Nimmo and Donara Barojan of the Atlantic Council, a think-tank. It begins in Syria, where a pro-Assad website published an article claiming that those who came to the aid of the attack’s victims were not wearing protective gloves, and therefore it must be a hoax. It also claimed that a TV station had inadvertently announced plans to cover the strike before it had taken place. This idea was then picked up by several websites, including the Centre for Research on Globalisation, a hub for conspiracy theories and fake stories.

From there it was a short hop to American conspiracy sites, such as Mr Jones’s Infowars, which claimed the whole thing was a “false-flag” operation funded by George Soros. Mike Cernovich, another conspiracy theorist, took a similar line and spread the phrase #SyriaHoax. It was given a bump by computer programs used to boost stories on social media (one Twitter account used #SyriaHoax 155 times). A foreign government might have had a hand in this: the Senate has heard testimony that Russia used this technique to spread fake news stories during last year’s election. Since April 6th, #SyriaHoax has been used in 192,000 tweets—85% of which originated in the United States. The hashtag reached 13.6m Twitter users in a single hour according to Keyhole, a social-media analytics firm. And that is how some self-publicists, posing as American patriots, became apologists for the Assad regime, which drops poison gas on children.

CORRECTION: An earlier version of this story said that Mike Cernovich has been praised by President Trump. That was wrong and has been removed. It was Donald Trump Jr. who said of Mr Cernovich, “in a long gone time of unbiased journalism he’d win the Pulitzer”. Sorry.