When the Civil War erupted in 1861, the lack of a formal battlefield evacuation system placed injured soldiers at risk of dying from their wounds. In June 1862, when Letterman assumed the position of Medical Director of the Army of the Potomac, the largest force in the Union Army, he instituted the Letterman Plan. Part of the plan called for the establishment of an Ambulance Corps to evacuate soldiers wounded during battles.
Letterman also created a tiered system to assess battlefield casualties. Once the men in the Ambulance Corps transported an injured soldier from the battlefield to a nearby aid station, assistant surgeons and medical attendants used tourniquets to limit the flow of blood and administered morphine or whisky for pain. After this preliminary round of care, doctors and attendees determined the severity of the wound and placed the injured soldier into one of four categories: severely wounded, mildly wounded, lightly wounded, or mortally wounded.
Soldiers with severe wounds, such as fractures, missing limbs, or severe bleeding, were marked as first priority and brought to a nearby field hospital for immediate medical care. If the soldier survived, they were transported to a hospital in a nearby city to recuperate and receive long-term care. Soldiers in stable condition with mild wounds were marked as second priority and remained at the aid station until all of the severely wounded soldiers were attended to and removed. Soldiers with minimal injuries that required bandages were marked as third priority. After receiving treatment, medical attendants ordered soldiers to return to their units. Soldiers that arrived at the aid station with mortal wounds to their head or chest were made comfortable, possibly received their last rites, and left to die.
During the Battle of Antietam on September 17, 1862, Letterman’s plan was tested. The tiered system proved successful when the Medical Department successfully removed 17,000 wounded soldiers from the battlefield within 24 hours. The system also withstood the heavy casualties from the Battle of Fredericksburg and the Battle of Gettysburg.
Today, we know Letterman’s tiered system as triage. It is used by Emergency Medical Services and combat medic units to apply the best form of care to as many people as possible.