For the whole of the war Claude Farrère was in the French navy. According to the Dictionnaire de Biographie Française (fascicule 75, 1972), upset with the inactivity of the navy, he asked for a transfer to a tank regiment in 1916. He took part in the first ever tank assault, at Berry-au-Bac, on April 16 1917, during the Second Battle of the Aisne. The assault was not a success: German artillery picked them off one by one. But at least Farrère survived. He was still technically in the Navy, until his resignation in October 1919.
Claude Farrère in the Great War