[4] In 1933 he assists to a conference by prominent French orator and militant Sébastien Faure which he describes in his own words as a "revelation" and afterwards he embraces anarchism and starts to participate in anarchist groups.
[4] During 1938 and 1939, he participated in solidarity with anti-fascist sides of the Spanish Civil War, and in 1939, he started his activities as an orator and writer with a conference on Max Stirner and his book The Ego and His Own, an author which would influence his thought profoundly.
[3] After the war Arru became the general secretary for the French section of International Antifascist Solidarity.
[8] From 1968 to 1982, Arru alongside the members of the Group Francisco Ferrer publishes La Libre Pensée des Bouches du Rhône.
[8] This publication included writings by authors such as Charles-Auguste Bontemps, Giovanni Baldelli, Jean Champagne, Jeanne Humbert, Albert Joël, Imbert-Nergal, Roger Monclin, Alain Kersauze, Albert Potvin, and Francis Ronsin.