Medicine, in World War I, made major advances in several directions. The war is better known as the first mass killing of the 20th century—with an estimated 10 million military deaths alone—but for the injured, doctors learned enough to vastly improve a soldier’s chances of survival. They went from amputation as the only solution, to being able to transport soldiers to hospital, to disinfect their wounds and to operate on them to repair the damage wrought by artillery. Ambulances, antiseptic, and anesthesia, three elements of medicine taken entirely for granted today, emerged from the depths of suffering in the First World War.

“In the early stages of the war, especially within six weeks, 300,000 French soldiers were wounded—and as competent surgeons were not to be had for more than a minority, an appalling number of needless amputations were made. In strictest confidence, Tuffier told me with tears in his eyes that more than 20,000 amputations had been made,” George Crile, a volunteer physician from Cleveland’s Lakeside Hospital, wrote in his diary in January 1915.

The key dilemma was that doctors had no effective antiseptic to kill the rampant bacteria, such as Clostridium perfringens, which causes the rapid necrosis known as gas gangrene. The soldiers lived in the filth of the trenches, and if they were wounded, their injuries were immediately corrupted with it. Théodore Tuffier, a leading French surgeon, testified in 1915 to the Academy of Medicine that 70 percent of amputations were due to infection, not to the initial injury.

“Professor Tuffier stated that antiseptics had not proven satisfactory, that cases of gas gangrene were most difficult to handle,” Crile wrote. “All penetrating wounds of the abdomen, he said, die of shock and infection. … He himself tried in fifteen instances to perform immediate operations in cases of penetrating abdominal wounds, and he lost every case. In fact, they have abandoned any attempt to operate penetrating wounds of the abdomen. All wounds large and small are infected. The usual antiseptics, bichloride, carbolic, iodine, etc., fail.”

Help was on the way from the Rockefeller Institute for Medical Research in New York. The French physician Alexis Carrel, who had been working at the Rockefeller Institute before the war, had signed up with the French army and was given an abandoned château in Compiègne, near the front, to renovate into a military hospital. He demanded an X-ray machine and laboratories for analysis. When the French Service Sanitaire declined to provide them, Carrel turned to the Rockefeller Institute. They sent equipment, and most important of all, they sent Henry Dakin, a British biochemist who had perfected a solution of sodium hypochlorite, which killed the dangerous bacteria without burning the flesh. Carrel took the new antiseptic and insisted on opening up wounds to thoroughly irrigate them. The technique, which became known as the “Carrel-Dakin Method,” was adopted by doctors across Europe during the war.

Over at the American Ambulance Hospital, meanwhile, George Crile was introducing doctors to a method of anesthesia he and a nurse named Agatha Hodgins had developed in Cleveland. In January 1915, their Lakeside Unit had begun a series of three-month rotations in Neuilly. Crile had brought with him 18 large cylinders—3,000 gallons—of nitrous oxide. He gave surgical demonstrations using a nitrous oxide-oxygen mix—just enough to put a patient to sleep, but not into a state of shock—for Carrel, Dakin, and other French surgeons.