In august 1914, at the start of World War I, blood transfusion remains quite infrequent, with rough methods, inaccurate indications and poor results. The direct surgical techniques of arteriovenous anastomosis proved ill-adapted to the emergency conditions of war wounds. Indirect techniques with syringes and storage tubes were frequently limited, and complicated, by blood-clotting. Moreover, despite Landsteiner's discovery of ABC blood groups in 1901, compatibility testing was poorly known and often considered unnecessary. At the beginning of the war, none of the belligerent armies'medical services was specifically organized for blood transfusion. In the early years of the war (1914-1916), blood transfusions remain rare. The first transfusion in the French army was performed by Emile Jeanbrau on 16 October 1914. The main impulse, however, came from surgeons of the Canadian Army Medical Corps (CAMC), who had learned about transfusion from doctors in the United States (Bruce Robertson, Edward Archibald). Transfusions became increasingly frequent, particularly as part of pre-operative preparation in cases of wound shock and hemorrhage. The last years (1917-1918) were marked by the arrival of the American Army in France, with a growing medical influence of American doctors. Oswald Robertson introduced the use of citrated blood in glass bottles, being subsequently called "the first blood banker". Blood transfusion remained throughout the war infrequent and technically imperfect. Wartime, however, by the efforts of some young Canadian and American doctors, was a tremendous opportunity for diffusion and improvement.