Users of Ironmarch.org have attempted a mall shooting; murdered two young men; attempted to hack a Sikh dentist to death with a machete; and have been found to be in possession of illegal weapons and materials to make bombs, among other crimes. While these acts of violence mostly took place in North America, the forum had plenty of fans in the UK.

Ironmarch.org was not the kind of website to hang out on if you knew what was good for you. A swastika-plastered forum which took its users on a shared journey of extreme radicalisation, it kickstarted an international wave of Nazi terror.

One of Ironmarch's administrators founded the banned British Nazi terror group National Action (NA), while an infographic produced by the site lists NA among its "affiliated groups", under the heading "Ironmarch members in the global fascist struggle".

One of the oldest and largest neo-Nazi forums – and linked to almost 100 hate crime murders in a report by the Southern Poverty Law Center – Stormfront had its domain name seized shortly after Charlottesville. Daily Stormer, meanwhile, was forced to move its domain registration repeatedly, before eventually losing it altogether and having to register at a number of other short-lived domain names.

Despite its frequent calls for violence, however, the forum never achieved the same notoriety as two other neo-Nazi websites – Stormfront and Daily Stormer, which both came under intense scrutiny last year after an alt-right demonstration in Charlottesville descended into violent clashes and an anti-racist protester was killed by a neo-Nazi.

The website disappeared in November of 2017, following reports that its founder had left. But as one of the main online forums advocating neo-Nazi terrorism, the bloodthirsty political current it helped to shape will live on.

IronMarch's "welcome" section boasted that it had been labelled the "Nazi Facebook" and had the slogan, "Gas the Kikes, Race War Now, 1488 Boots on the Ground!" (1488 refers to the Nazi "14 words" and "Heil Hitler" – "H" being the eighth letter of the alphabet.)

The website was started in 2008, intended as an explicitly fascist online message-board. Instead, it ended up becoming a forum for the International Third Position Federation (ITPF), an extreme right-wing group that emerged in the UK in the 1980s around former BNP leader Nick Griffin. Most early members had left the group behind by the late-1990s, and by 2008 it was irrelevant, making membership of an ITPF internet forum an incredibly niche pursuit.

Stormfront was always a site for all kinds of neo-Nazis, while Daily Stormer acted as bridge between extreme neo-Nazis and sections of the alt-right. Ironmarch was different.

Mason revered Charles Manson, the notorious serial killer who carved a swastika into his forehead and died in 2017. Manson told Mason to start a neo-Nazi group called "Universal Order", and to make its logo a swastika superimposed over some scales, so that's exactly what Mason did.

Mason is an elderly American neo-Nazi who was briefly linked to the Church of Satan, before getting involved with the American Nazi Party and the National Socialist Liberation Front (NSLF), which was responsible for three bombings in the Los Angeles area in 1975.

In July of 2017, members of the Atomwaffen Division – the neo-Nazi paramilitary group launched by Ironmarch users in the US – used the forum to announce they had met with Mason and were going to help him resume publishing SIEGE. A banner appeared on the site announcing "JAMES MASON IS BACK!", which linked to a thread containing an interview with Mason. A user called "Rape" said of his meeting with the neo-Nazi: "My road trip was worth the thousand miles." Another user said Mason had "100 percent endorsed" Ironmarch and Atomwaffen. Since encouraging Mason to return to active neo-Nazi politics, Ironmarch users have started a website for him and produced a number of videos promoting him and his views.

The SIEGE newsletters were published in a book, also called SIEGE, which was discovered by Ironmarch users and quickly became one of the key texts the forum encouraged its users to read. Ironmarch described finding the book as "something of an 'ah ha!' moment for us", and has even published its own edition, which it says has been dowloaded more than 16,000 times.

In 1980, Mason began publishing a newsletter called SIEGE, which advocated armed struggle and terrorism, and celebrated serial killers and mass-murderers. Publication ended in 1986 and Mason disappeared from public view, but his ideas did not.

About two years after Ironmarch users discovered Mason’s writings, some began to act on the ideas they promoted.

In early 2017, four members of Atomwaffen were living together in a shared property in Tampa, Florida. One of them, Devon Arthurs (known as TheWeissewolfe on Ironmarch), converted to Islam and killed two of the other members, later telling police they had insulted his religion. The surviving member of the group, Brandon Russell (known as Odin on Ironmarch), was arrested by police when they turned up at the property and discovered the group had been stockpiling illegal weapons and materials they could use to make bombs. Arthurs told police that Russell had been planning to throw explosives into a nuclear power plant, and he was sentenced to five years in jail in January of 2018 for possessing bomb-making materials.

In February of 2015, a Columbine-obsessed American goth called Lindsay Souvannarath flew to Canada to visit two friends she had met on tumblr. The three were planning to head to a mall in Halifax on Valentine's Day to kill as many people as they could, using a rifle, a shotgun and gas bombs. When Souvrannarath arrived in Canada she was detained by police, and later pled guilty to conspiracy to commit murder. The court heard that "Souvannarath had a pre-existing interest in school shootings and Nazism".