The death of Caesar’s legates, Sabinus and Cotta, with their fifteen cohorts in 54 BC is the most significant defeat of Roman armies in Gaul. In his Commentarii, Caesar presents this setback as the result of one man’s fault : his legate Q. Titurius Sabinus. Behind Caesar’s propaganda, the tale of the clades Tituriana provides a rich source of information for an analysis of Roman legionaries combat experience. As it tells the story of an inevitable defeat, Caesar’s text provides details shaping the contours of this experience. The use of modern military psychiatry combined with an anthropological approach allows the reader to better identify the efficiency of the Roman legions and also their weaknesses and vulnerability.