Scott McGaugh

Jonathan Letterman was an outpost medical officer serving in Indian country in the years before the Civil War, responsible for the care of just hundreds of men. But when he was appointed the chief medical officer for the Army of the Potomac, he revolutionized combat medicine over the course of four major battles-Antietam, Fredericksburg, Chancellorsville, and Gettysburg-that produced unprecedented numbers of casualties. He made battlefield survival...