Ancient Roman civilization is generally known and appreciated for its military strength and for its ability to give a rule to different nations and to keep united and prosperous for some centuries several peoples all along the shores of Mediterranean Sea. As a consequence Roman leaders are conceived of essentially as warriors and generals and stress is conveyed on their military courage and competence. This is incorrect. The first skill they needed to possess, was rhetoric, not the useless ability to build up literary discourses but the skill of persuading Senate and Roman people on the convenience and utility of their military and civil projects ( what included the objective validity and the technical feasibility of these) and of persuading legionaries and auxiliaries in the difficult moments of a campaign. Roman generals ( duces, legati, centuriones ) could not rely upon any organization that would compel soldiers to obey their leaders and fight valiantly. The only punishments and gratifications that existed, were to be administered on the spot by the very legions on the field. If a general mutiny exploded, the general was lost and with him his army. The only mean he could rely upon was his personal speech made strong by a convenient rhetoric. The Roman general Julius Agricola, that valiantly fought against Britons is represented by Tacitus as endowed with a rhetoric skill, that gave him the power to control his army and to duly excite his soldiers before the fight. But Tacitus supposes that also the Briton leaders had an heroic rhetoric of their own, that he renders in the shape of Latin language (Tacitus, De vita Julii Agricolae 30-35) . The rhetoric of discourses pronounced both by Roman and Briton leaders and referred by Tacitus deserves much attention by students of linguistic means of persuasion.