In spite of an early British emphasis on battlefield psychiatry and an American attempt to exclude men with psychiatric illness from military service, mental illness remained a major cause of combat disability, with about 30 percent of Allied combat zone casualties being psychiatric. Although physicians in World War I had learned that treatment close to the front lines made it possible to return a number of psychiatrically disabled soldiers to combat, the lesson was forgotten. Early in World War II, patients with combat fatigue were routinely evacuated to rehabilitation hospitals, and most were discharged. As manpower became scarce, more of these men were placed in pioneer or labor details in the rear area, but few returned to combat.
Captain Frederick R. Hanson, an American neurologist and neurosurgeon who had joined the Canadian army early in the war and participated in the landing at Dieppe, transferred to the U.S. Army and developed what became a successful and widely employed treatment for what the British now termed exhaustion or combat fatigue. The essential parts of the regimen included sedation, brief periods of rest, and treatment in a facility close to the front, where the patients and staff continued to wear combat clothing. Hanson realized that treating these patients as if they were mentally ill and physically separating them from their units made it unlikely that they would return to duty. Using his treatment protocols, the British and American armies were able to return 70 to 80 percent of combat fatigue victims to their units, and only 15 to 20 percent of patients requiring evacuation to the zone of the interior were psychiatric.
Shortly after the Italian invasion, the U.S. Army established the post of division psychiatrist, and Hanson produced a manual for internists so nonpsychiatrists could use his methods. As the war went on, Allied military psychiatrists became convinced that no soldier was immune from combat fatigue. They hypothesized that any man subject to continuous combat for a long enough time would become nonfunctional and estimated that 200 days of constant action was about the maximum a soldier could be expected to tolerate. The British adopted a system of unit rotation to give their men regular periods of rest and were able to stretch the tolerable period to close to 400 days, but the Americans, except in the U.S. Army Air Forces, adopted a more haphazard approach of rotating individuals with the longest periods of service rather than entire units. It was not until later wars that regular unit rotation became standard.
Military physicians, mindful of the heavy clinical and financial burden of long-term psychiatric illness after World War I, correctly warned that the true cost of combat fatigue would not become evident until after the soldiers returned to civilian life.
Cowdrey, Albert E. Fighting for Life: American Military Medicine in World War II. New York: Free Press, 1994.; Slight, David. "Psychiatry and the War." In William H. Taliaferro, ed., Medicine and the War, 150–171. Chicago: University of Chicago Press, 1944.