At the time of the Liberation, in September 1944, with the assistance of officer Pierre Dunoyer de Segonzac, he founded the newspaper Debout[3][4] (Standing Up or On Our Feet) in Castres, in accordance with the motto of the city.

He writes La Révolution Cubaine (The Cuban Revolution) in 1961, which becomes the first book published in France dealing with this major event of Latin America's contemporary history.

[3] Reacting against a common preconception, he publishes the stand out book L'Empire Américain (America's Empire) in 1968, which will receive the French literary award of the Prix Aujourd'hui.

Very well documented, the book will remain for a long time as "the indispensable instrument to the understanding of contemporary international politics".

[1] In January 1973, he succeeds François Honti as the director of Le Monde diplomatique (meaning "The Diplomatic World" in French), of which he will considerably increase the circulation and readership.

"Claude Julien transforms Le Monde Diplomatique into a more incisive organism, offering to more numerous readers meticulous analyses of the major international, social, economic and cultural issues.

[10] In June 1980, the Society of Editors of the newspaper Le Monde elects four candidates, of which Claude Julien, to succeed director Jacques Fauvet.