The 34-year-old was one of eight members of the terrorist group to be convicted in a series of trials that dismantled its Midlands cell.
But terror police warned that the threat would not go away and predicted that “peripheral” figures would start chapters under new names.
When police raided Vehvilainen’s accommodation in Sennybridge Camp, Powys, in September 2017 they found swastika flags, Nazi memorabilia, CDs of Third Reich music and stockpiles of knives, guns and other weaponry.
He had constructed a “crudely made device" which resembled a homemade electromagnetic pulse (EMP) - intended to disrupt electronic equipment.
Birmingham Crown Court heard that he had also written notes on terror attacks, sparking civil disorder and the destruction of national infrastructure and drafted a magazine called Extinction, which urged readers to be “ready to fight and die for your race”.
Through his work as an army trainer, he tried to bring what he called “committed Nazis” over to National Action, introducing at least three soldiers to encrypted chat groups including one called “Triple K Mafia”, the jury was told.
As well as racist, antisemitic and genocidal comments in chats with his fellow National Action members, he used a pseudonym to post vile rants online.
One called black people n*****s and “pack animals” and vowed to “fight the Jew forever”.
Another said white people “shouldn’t be on the same planet” as black people, adding: “The sooner they're eliminated the better.”
The court heard that Vehvilainen was considered an “outstanding soldier” while serving in Afghanistan, but he claimed that “when I was involved in killing [Muslims] it didn’t bother me one bit”.
In the same message, from February 2017, he wrote: “How anybody can somehow regard n*****s and w**s as human beings and worthy of life is beyond me. I could shoot their children and feel nothing.”
Messages showed Vehvilainen express his desire for bloodshed time and again, with one reading: “Every part of me wants war. There is no other way.”
He told a co-defendant that his Army camp contained “a good group of fully committed men with our beliefs”.
The soldier added: “We also have other contacts on other bases and a lot of people are slightly sympathetic to our ideas. We also have good opportunities to get more equipment, uniforms etc.”
Vehvilainen and his fellow extremists were hatching a plan to turn depopulated rural villages into a “national socialist community”.
He planned to recruit enough soldiers to ensure “we’ll be in the right place when things start to collapse”, while stealing Army equipment and rations.
Among his targets was Private Mark Barrett, who was acquitted of terror charges earlier this year but has been discharged from the Army.
Colonel Graham Taylor, of the Army Personnel Services Group, said: “Far-right ideology is completely at odds with the values and standards of the Army and whilst we are only talking about a very small number of cases we take this issue very seriously. We have robust measures in place, including during the recruitment process, to ensure those exhibiting extremist views are neither tolerated nor permitted to serve. Any soldier receiving a custodial sentence will be discharged from the Army.”
Detective Chief Superintendent Matt Ward, head of the West Midlands Counter Terrorism Unit, said the group had spent years planning for a race war.
“Vehvilainen’s role typified the progress that National Action wanted; he was a non-commissioned officer in the British Army with access to young men who could be radicalised and recruited into the group,” he added. “He was an incredibly dangerous individual and a key part of the National Action strategy.”
He was jailed for eight years in April alongside Alex Deakin, who received the same term for his role as regional coordinator for National Action.
The men’s convictions for membership of a proscribed group could be reported for the first time on Monday after the trial of their fellow extremists ended.
Fanatical neo-Nazi couple Adam Thomas, 22, and Claudia Patatas, 38, were convicted of National Action membership alongside Daniel Bogunovic, 27.
A jury at Birmingham Crown Court was told the couple had given their child the middle name “Adolf”, which Thomas said was in “admiration” of Hitler, and had Swastika scatter cushions in their home.
Photographs recovered from their home also showed Thomas, who failed to get into the Army twice, cradling his new-born son while wearing the hooded white robes of a Ku Klux Klansman.
Three other men who had been due to stand trial alongside the trio - Thomas' close friend and goods vehicle driver Darren Fletcher, 28, IT worker Joel Wilmore, 24, and van driver Nathan Pryke, 26 - all admitted being National Action members before proceedings began.
The group became the first far-right group ever banned in the UK in December 2016, when the government condemned its “racist, antisemitic and homophobic” ideology.
National Action split into a series of regional factions that operated under new names in an effort to dodge the prohibition, but its followers have been rounded up in waves of arrests and two aliases – NS131 and Scottish Dawn – have been banned in their own right.
Det Ch Supt Ward said the eight extremists convicted “were not simply racist fantasists”.
He added: “We now know they were a dangerous, well-structured organisation,” he added. “Their aim was to spread neo-Nazi ideology by provoking a race war in the UK and they had spent years acquiring the skills to carry this out. They had researched how to make explosives. They had gathered weapons. They had a clear structure to radicalise others. Unchecked they would have inspired violence and spread hatred and fear across the West Midlands.”
He also warned that although the convictions had dealt a significant blow to National Action and dismantled its Midlands chapter, the threat they pose will not go away.
”Others on the periphery will take on leadership roles and so I ask for the public’s vigilance,” Det Ch Supt Ward said. ”We have seen many convictions over the past few years in connection with Syria-related terrorism and this work continues apace. But extreme groups such as National Action also have the potential to threaten public safety and security.”