US Army nurses and medics remove a bandaged soldier from a C-47 transport plane to an ambulance during a rehearsal for D-Day. PhotoQuest/Getty Images Intense fighting and high casualties in Ukraine have raised new challenges for military medicine. This summer, the US and Chinese militaries both trained on new ways to evacuate wounded troops. In a long-range war in the Pacific, medevac operations will be more difficult to conduct. For most of American military history, medical evacuation meant a long, painful ride in a horse-drawn wagon or a rudimentary vehicle. Since the Korean War, US soldiers have become accustomed to...