In 1917, as war raged in Europe, Oswald Hope Robertson studied the workings of blood at Massachusetts General Hospital. His graduate work looked at pernicious anemia, a lack of red blood cells, and he had also studied the new science of clotting, especially as it affected how blood could safely be transferred from one patient to another. 

Blood transfusion at the time had hit a wall. Most transfusions were performed much as they had been in 1818, when the first successful transfusion occurred. Blood from one patient was directly given to another, because blood would clot if left outside the body for too long. Sometimes a surgeon would directly suture the blood vessel of a donor to that of a recipient with silk or human hair.   

In April 1917, the United States entered World War I, and Robertson was called into service as a member of the Army Medical Corps. Blood loss on the battlefield was a leading cause of death, and French and British doctors had been experimenting with new transfusion techniques. But battlefield conditions didn’t allow for the delicate, direct procedures that hospitals used. Robertson was asked to find alternatives. 

His idea was simple. The medical corps would look for volunteers—usually lightly wounded soldiers—with type O blood, which could safely be given to most soldiers regardless of their blood type. Each would donate about two cups of blood, which would be put in a bottle and treated with sodium citrate, recently shown to be an effective anticoagulant. The bottles would be stockpiled near the fighting in ammunition boxes, and packed with sawdust and ice, which helped them to keep for a few weeks. 

The result was the first “blood depot”—the precursor of the modern blood bank—in 1917. The system was put to the test in the Battle of Cambrai on the Western Front. Not all soldiers who received the transfusions from the blood depot survived. But by March of the following year, hospitals of the American Expeditionary Forces were convinced of the depots’ usefulness and officially adopted Robertson’s method.

Transfusion kits were soon taken into the field, allowing medics to give blood quickly to soldiers in shock. Throughout the rest of the war, Robertson gathered data about which patients benefited the most, adding to wartime research on blood transfusion that facilitated its widespread adoption when the war ended.

The blood depots became the blood banks of civilian medicine. Each day, according to the American Red Cross, patients in this country use 7,000 units of blood—making Robertson’s technology one of the greatest peacetime dividends to come out of a global conflict.