War is sometimes mistakenly construed as the chief impetus for medical innovation. Nevertheless, military conflict obliges the implementation of discoveries still at an experimental stage. Such was the case with the practice of blood transfusion during the Spanish Civil War, when massive demand for blood provoked immediate recourse to breakthroughs in transfusion medicine not yet integrated into standard medical practice. The Spanish Civil War marked a new era in blood transfusion medicine. Frederic Dur'an-Jord a and Carlos ElÃ3segui Sarasoles, directors, respectively, of the blood transfusion services of the Republican Army and of the insurgent forces, were innovators in the field of indirect blood transfusion with preserved blood. Not only had they to create transfusion services, almost from scratch, capable of supplying campaigning armies with blood in wartime conditions, they also had to struggle against the medical establishment and to convince their medical peers of the value (not to men