There's a condition in combat—most people know it by now. It occurs when a soldier's nervous system has reached the breaking point. In World War I, it was called shell shock. Simple, honest, direct language. Two syllables. Shell shock. Almost sounds like the guns themselves. Shell shock!!
Source: wiktionary
I passed through the shell-shock wards and a yard where the "shell-shocks" sat about, dumb, or making queer, foolish noises, or staring with a look of animal fear in their eyes.
Source: wiktionary
Of the 79 officer casualties 10 were "shell-shocks", or about 12 per cent, of the whole. Of the 10 shell-shocks 4 were sent to C.C.S. and 6 to Corps Rest Station.
Source: wiktionary
Most nurses found the helplessness of "the shell shocks" painful and "pitiful."