During his trial, he said he had been “just blowing hot air” online and that none of the plans discussed “seemed real”, but he was convicted of preparing acts of terrorism.
A jury also found him guilty of disseminating terrorist publications through an online “library” that encouraged attacks.
Cronjager previously pleaded guilty to four offences of possessing information useful to a terrorist, over documents containing instructions on how to kill people with your bare hands, make explosives and create homemade firearms.
Sentencing him on Tuesday, the Recorder of London said that by the age of 17 Cronjager “supported the extreme right-wing cause” and was “committed to violence”.
“In your own words, you held fascist beliefs and wanted to bring about a change of government by violence,” Judge Mark Lucraft QC.
“You expressed hatred for people with a different skin colour, Jewish people, Muslims and those with different sexual orientation than your own. You wanted a revolution based on your racial ideology.”
The judge said the teenager prepared acts of terrorism by attempting to procure a 3D-printed gun, drawing up plans for a weapons storage bunker and by providing instructions to other like-minded young
neo-Nazis.
The court heard that Cronjager was arrested at his family home in Ingatestone, Essex, in December and had committed the offences during autumn last year.
Police found knuckle dusters and body armour in a wardrobe, and hand-drawn plans for the bunker.
A large collection of extreme right-wing propaganda, bomb instructions and combat manuals was discovered on his digital devices.
Cronjager did not know that one of the extremist groups he was part of on the encrypted
Telegram messaging app -
the British Hand - had been infiltrated by an undercover police officer.
He sent the officer money and instructions to be used by a contact to 3D-print a gun, while voicing his violent wishes.
The Old Bailey was shown online messages where Cronjager told the officer he wanted to murder a former friend, who was Asian, after being told he was having sex with a white girl.
“I’ve found someone I want to execute,” Cronjager wrote. “He’s a sand n****** that f***ed a white girl. In fact I think three of them.”
The teenager discussed using a conventional shotgun, or manufacturing 3D-printed firearms for himself and “the rest of the lads”.
In a victim impact statement read to the court, the boy said he had been best friends with Cronjager and “trusted him more than anyone else”.
The teenager told how when police initially alerted him he thought it was a joke, but then the “realisation broke my heart”, and left him with long-term psychological problems.
Cronjager was in contact with a
neo-Nazinamed only under the pseudonym “Bull”, who was the international leader of Exiled 393 and told Cronjager to organise storage for an incoming shipment of conventional guns.
He drew plans for a storage bunker with labelled sections for mortars, rifles, pistols and ammunition, along with food, water and clothes for the terrorists who would use them.
