Or combat neurosis or battle fatigue; Any of the various forms of mental disorder that affect soldiers exposed to heavy explosions or extreme stress. Shell shock was first diagnosed during World War i.
At first thought to be a physical condition due to blast and carbon monoxide poisoning, it was realised during the course of World War I that the symptoms—mental confusion or frenzied terror—were neurotic in origin, similar to those found after civil accidents such as train wrecks or factory explosions. Most soldiers returned to normal after a rest away from the front line, but some never recovered and exhibited peculiarities of gait, hysterical loss of voice or sight, paralysis of limbs, and other symptoms.
Following the Vietnam War, many veterans were found to be suffering from post-traumatic shock syndrome, in which recurring “flashbacks” to combat experiences torment the sufferer.