Jean-Charles Augustin Bernis was a French officer, he took part in the First and in the Second World Wars. Colonel of the French Army, Supreme Commandant of the Public Force (Force Publique) in 1936 -1940. He was active member of the French Resistance, one of the founders of the intelligence net "Alliance", led by Georges Loustaunau-Lacau and Marie-Madeleine Fourcade. Colonel Bernis was arrested in Monaco in the beginning of 1943. After the Second World War he was an active member of the veteran organizations of the French Resistance. Colonel Bernis was a theoretician of the military intelligence, author of the book "Le Service de Renseignement, le rôle et la méthode des 2èmes Bureaux en campagne" with the foreword of General Weygand, published 1934. In discussing the general question of military intelligence in time of war, the author starts from the undisputed premise that information of the enemy is absolutely essential and must be available in time for use. In any situation there are three factors involved; namely: 1.) the mission as laid down or deduced; 2.) the possibilities which our forces can execute; 3.) the possibilities which the enemy can execute. Colonel Bernis expertly illustrates his conception of how military intelligence should be handled by examples drawn from the Napoleonic Wars, Franco-Prussian War of 1870, and the First World War.