By the time Jonathan Letterman was promoted to major and made medical director of the Army of the Potomac in 1862, he had already been a military doctor for more than a dozen years. In that time he had served on the New Mexico frontier, where he had ample opportunity to witness the devastations of combat. The traditional practice was to wait until a battle was finished to collect the wounded. By that time it was often too late to help them.
As medical director during the Civil War, Letterman immediately began a complete restructuring of his resources from the bottom up. Among his many improvements, he brought the ambulance corps, which had taken its commands from a non-medical department, under his management. He made sure the customized ambulance wagons were supplied with stretchers, bedding, kettles, food, wound dressings and other medical supplies [source: U.S. Army].
Letterman realized that a key element to surviving trauma was speed. His ambulance corps must evacuate the wounded from the battlefield, provide basic first aid and get them to a medical facility as fast as possible. The procedures he set up to accomplish these feats are known as the Letterman System, and the principles behind it are used by emergency medical responders to this day. After the Battle of Gettysburg, the entire Union Army adopted the Letterman System.
The medical officers who deployed the Letterman System during the Spanish-American War of 1898 realized they could improve outcomes further by having the stretcher bearers apply bandages before they even moved the wounded. By World War I, the role of these field-dressing stretcher-bearers had become so crucial their role was formalized as army medics. As non-medical personnel trained to apply basic first aid on location, these medics were the direct prototypes for today's emergency medical responders [source: Margolis].