One of main the figures of post-WWII nationalism in France, Sidos was the founder and leader of the nationalist organizations Jeune Nation (1949-58) and L'Œuvre Française (1968-2013).
Sidos was convicted in 1946 for joining the fascist Mouvement Franciste at 16 years old in the midst of WWII and Nazi occupation of France.
After spending two years of internment in Natzweiler-Struthof, he founded in 1949 Jeune Nation, the most prominent French neo-fascist movement of the 1950s.
Famous for its insurrectional violence during the Algerian war, the organization was dissolved by official decree in 1958.
Convicted a second time in 1963 for "recreating a disbanded league" and "compromising State security", Sidos founded Occident the following year, but soon broke with the group.
He eventually established another Vychist movement in 1968, L'Œuvre Française, of which he was the leader until he stepped down in 2012.
The movement was banned a year later, making it the fourth association founded by Sidos to be dissolved by the French authorities, and the fifth he had been part of, in a 70-year period of nationalist and crypto-fascist activism.