This article documents a rare surviving material testimony of a battlefield blood transfusion performed during the First World War. The study reconstructs a “heroic” father-to-son arteriovenous transfusion carried out in Cherbourg Naval Hospital on January 24, 1915. Analysis of the preserved glass cannula highlights an original French adaptation of the Alexis Carrel transfusion method. The paper explores the evolution of early transfusion technologies and vascular techniques before the standardization of modern blood banking. This memorial object illustrates the intersection of wartime surgery, medical innovation, and personal memory in the history of military medicine.