Werth was born in 1878 in the Remiremont, Vosges, in an assimilated Jewish family. His father, Albert, was a draper and his mother, Sophia, was the sister of the philosopher Frédéric Rauh.
He was a brilliant student, a Grand Prize winner in France's Concours général and a literary and humanities CPGE philosophy student at Lycee Henri IV. However, he abandoned his studies to become a columnist in various magazines. Leading a bohemian life, he devoted himself to writing and art criticism.
Werth was a protégé and friend of Octave Mirbeau, the author of The Diary of a Chambermaid, completing Mirabeau's final novel, Dingo, for him when the author's health failed. He manifested his anti-clericalism as an independently-minded anti-bourgeois anarchist. He just missed the Prix Goncourt in 1913 for his novel La Maison blanche (The White House), which Mirbeau prefaced.
During the First World War, in 1914 he was assigned to the front, where he would fight for 15 months before being wounded. It was at this time he became a pacifist. He would shortly write Clavel Soldat, a pessimistic and virulently anti-war work which caused a scandal when it was released in 1919.
Werth was an unclassifiable writer with an acid prose, who wrote of the inter-War period as well as advocating against colonialism (Cochinchine, 1928). He also wrote against the colonial period splendor of the French empire, and against Stalinism which he denounced as a leftist deception. He also criticized the mounting Nazi movement.
After the Fall of France, during its occupation, the Werths remained in France despite offers by the Centre americain de secours in Marseille to help them emigrate. In July 1941 Werth was required to register as Jewish, his travel was restricted and his works banned from publication. His wife, Suzanne, was active in the Resistance, crossing the demarcation line clandestinely more than a dozen times and establishing their Paris apartment as a safe house for fugitive Jewish women, British and Canadian pilots, secret resistance meetings and storage of false identity papers and illegal radio transmitters. Their son, Claude, continued his studies first in the Jura and then in Paris, later becoming a doctor. Werth lived poorly in the Jura Mountain region, alone, cold and often hungry. Déposition, his diary, was published in 1946, delivering a damning indictment of Vichy France. He became a Gaullist under the Nazi occupation and after the war contributed to the Liberté de l'Esprit intellectual magazine run by Claude Mauriac. Werth died in Paris on 13 December 1955.
Antoine de Saint-Exupéry
Saint-Exupéry met Werth in 1931. Werth soon became Saint-Exupery's closest friend outside of the flying group of his Aeropostale associates. Werth did not have much in common with Saint-Exupéry; he was an anarchist, his father was a Jew, and a leftist Bolshevik supporter. Being twenty-two years older than Saint-Exupéry, with a surrealistic writing style as well as the author of twelve volumes and many magazine pieces, he was Saint-Exupéry's very opposite.
Saint-Exupéry dedicated two books to him, ("Letter to a Hostage" and "The Little Prince"), and referred to Werth in three more. At the beginning of World War II, while writing "The Little Prince", Saint-Exupéry lived in his downtown New York City apartment, thinking about his native France and his friends. Léon Werth spent the war unobtrusively in Saint-Amour, his village in the Jura, a mountainous region near Switzerland where he "was alone, cold and hungry", and had few nice words on French refugees. Saint-Exupéry returned to the conflict by joining the Free French Air Force in early 1943, rationalizing, "I cannot bear to be far from those who are hungry... I am leaving in order to suffer and thereby be united with those who are dear to me."
At the end of the Second World War, which Antoine de Saint-Exupéry didn't live to see, Léon Werth said: "Peace, without Tonio (Saint-Exupéry) isn't entirely peace." Leon Werth did not see the text for which he was so responsible until five months after his friend's death, when Saint-Exupéry's French publisher, Gallimard, sent him a special edition. Werth died in Paris on 13 December 1955.
The Little Prince dedication
To Leon Werth
I ask children to forgive me for dedicating this book to a grown-up. I have a serious excuse: this grown-up is the best friend I have in the world. I have another excuse: this grown-up can understand everything, even books for children. I have a third excuse: he lives in France where he is hungry and cold. He needs to be comforted. If all these excuses are not enough then I want to dedicate this book to the child whom this grown-up once was. All grown-ups were children first. (But few of them remember it.) So I correct my dedication:
To Leon Werth, When he was a little boy
33 jours posthumous publication
33 jours (33 Days) is Werth's memoir of l'exode (the exodus) during the Fall of France. The title refers to the period of time he, his wife and their son's former nanny spent on the road during their flight from Paris to their summer home in Saint-Amour in the Jura region. (His son, then 15, and teenage friends covered the distance in less than a day by leaving several hours earlier, thus avoiding the mandated detours described by Werth. But, like so many parents during the exodus, the couple had no news of their son until reunited a month later.) With poetic economy and a journalist's precision he recounts his experiences as one of the estimated 8 million civilians who fled the advancing German army's invasion of Holland, Belgium, Luxembourg and France in May–June 1940. Werth gave the manuscript to his friend Saint-Exupéry in October 1940 to smuggle out of France, write a preface and publish in the U.S. The New York publisher Brentano's bought the rights (for a military parcel of cigarettes, gum, chocolates and water-purification tablets) and publication was planned for 1943, in expectation of which Saint-Exupéry referred to it as "un grand livre" (an important book) in his 1942 novel Pilote de guerre.  For reasons unclear it was never published, and the manuscript effectively disappeared.
Saint-Exupery's Letter to a Hostage was originally written to serve as the preface to Werth's 33 Days.
It was not until 1992 that Viviane Hamy found the missing manuscript and published it. Hamy led a rediscovery of Werth and later had many of his works republished in the 1990s and 2000s. Various events were organized in 2005 to commemorate the fiftieth anniversary of Werth's death.
title translations in italics:
- 33 jours (33 Days)
- Clavel chez les majors
- La maison blanche (The White House)
- Clavel soldat (Clavel soldier)
- Le destin de Marco
- Le monde et la ville (The World and the City)
- Saint-Exupéry, tel que je l'ai connu (Saint-Exupéry as I knew him)
- Caserne 1900
- Déposition / Journal 1940 - 1944
- Voyages avec ma pipe (Travels With My Pipe)
- Une soirée à L'Olympia
- Claude Monet
- Un soir de cirque
- Pierre Bonnard
- Les amants invisibles
- Chana Ourloff
- Cour d'assises
- Danse, danseurs, dancings
- Dialogue sur la danse
- Dix-neuf ans
- K.X. Roussel
- Impressions d'audience : le procès Pétain
- Meubles Modernes
- Le monde et la ville
- La peinture et la mode
- Pijallet danse
- Yvonne et Pijallet
- Une soirée à l'Olympia, livre electronique
- Léon Wert on the website of Viviane Hamy Publishing house
- Left french newspaper Politis, january 2006
- Events in the Pompidou Center Library in Paris
- Pierre Michel, Octave Mirbeau et Léon Werth.
- Heuré, Gilles. L'Insoumis. pp. 251–258.
- Antoine de Saint-Exupéry. The Little Prince, New York City: Reynal & Hitchcock, 1943.
- 33 jours.
- Diamond, Hannah (2007). Fleeing Hitler. Oxford: Oxford University Press. p. 150.
- Heuré, Gilles. L'Insoumis. Paris: Viviane Hamy. pp. 245 ff.
- Werth, Léon (2002). 33 jours. Paris: Editions Magnard. p. 8.
- Gilles Heuré, L'insoumis: Léon Werth, 1878-1955, Paris: éditions Viviane Hamy, 2006, ISBN 2878582195, ISBN 978-2878582192