 When he turned nineteen years old, at the end of 1916, he was mobilized into the military.He found himself in various units before being assigned to the colonial infantry front in the 5th Senegalese Tirailleur Battalion and fought in the Battle of Chemin des Dames.At the end of the war, de Cazenave returned to Haute-Loire and married in 1920 to Marie, a postmistress with whom he had three sons.