Fronten was an organ for the short-lived National Socialist Workers' Party of Norway, and Nielsen was skeptical to Nasjonal Samling.
[1] During the occupation of Norway by Nazi Germany, Nasjonal Samling people assumed political office.
He was set to administer the ownings of the Norwegian Order of Freemasons after it was closed down, and worked as an Anti-Freemasonry consultant for the Sicherheitsdienst.
[1] During the legal purge in Norway after World War II he managed to get his case delayed until 1950,[2] after first having been arrested between 13 May 1945 and 1946.
[4] Money was channeled to a foundation Arkitekt Eugen Nielsens Stiftelse, which among others supported Arnfinn Moland with 50,000 kr to write the strongly Nazi-critical book Over grensen?