From p108 of their book Shell Shock to PTSD: Military Psychiatry from 1900 to the Gulf War (ISBN 1841695807):
“As regards to the related question of how those diagnosed with psychiatric disorder actually performed in [World War II] combat, Plesset (1946) followed up 138 soldiers who in training had shown ‘sufficient adjustment difficulty to necessitate psychiatric attention’. After 30 days of combat, 137 remained on active duty, and one had received a gallantary medal. By the end of the war, 120 remained on active duty and eight had been awarded Bronze stars.”
Screening for those likely to suffer combat-related psychiatric disorder is one of the ‘holy grails’ of military psychiatry.
So far, this has proved impossible, as the single most important factor in predicting whether a soldier is likely to suffer combat stress reaction is the intensity of the fighting, rather than whether they have a history of mental illness.
Link to review of Jones and Wessely’s Shell Shock to PTSD.