During the First World War, several billion French letters and postcards were sent on both sides of the front. Politicians and the military headquarters quickly realized the determining influence of letters on the troops' morale. Communication analysis of the function of these written messages from this perspective seems relevant for at least four reasons: to describe the front as an ethnographic study of the war; to recount the horror of war as a therapeutic release; to study the letters as a means of circulating information between the front and the rear; and to capture these communication exchanges as organizational vectors between the front and the rear.