What is shell shock?
Shell shock
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Shell shock is a term coined in World War I to describe the type of posttraumatic stress disorder many soldiers were afflicted with during the war (before PTSD itself was a term).[2]  
It is a reaction to the intensity of the bombardment and fighting that produced a helplessness appearing variously as panic and being scared, flight, or an inability to reason, sleep, walk or talk.[3]