In 1929, Jean-Norton Cru, a French teacher of literature in the United States and a veteran of the First World War, published Témoins in France. The book recorded a resounding success and was discussed by veterans and writers. It is a kind of enormous bibliography (more than 300 authors) and a reflection about act of witnessing. Norton Cru also pretends to prepare the work of future historians. This article explores Cru’€™s criteria for “€œeffective witnessing”, the secrets of his classifications and administrative methods of proof. The second part of this article compares Cru’s concept of witnessing with the concept of professional historians of the time. After analyzing the stance presented in contemporary history (especially concering the Great War) in the principal historical reviews of the day (Revue historique, Revue de synthèse historique, Revue d’€™Histoire Moderne et Contemporaine) one can compare the methods of appreciation and judgment used by these reviews and those of Norton Cru. Could we say that after the war, French historians came back to a traditional concept of history (discussed before the war) where establishing the facts is the main duty of the historian?