A research in the National Archives of London made it possible to examine the letter, dated the day of the Austro-German Caporetto offensive, from Luigi Cadorna, Chief of Staff, to his British counterpart William Robert Robertson. Starting from Cadorna's considerations, the authors investigate the complex dynamics of relations between “non-friendly” allies of the Entente, against the background of the particularly difficult relationship, common to all European states at war, between military personnel and politicians in the conduct of the conflict, which finally saw a prominence of the latter ones.