In 1918, the final year of the First World War, American playwright Eugene O'Neill, then twenty-nine years old, went to Provincetown, Massachusetts, where a summer colony of writers congregated. Each year, some of the group, calling themselves the Provincetown Players, staged a series of original one-act plays. O'Neill had contributed plays for this series before, and this year he had written one called Shell Shock, which explored the dramatic possibilities of this psychological phenomenon that was in the news. He was better suited than many writers to tackle such a project. With one suicide attempt behind him, good friends having already succeeded, and having had to deal with the problems of his morphine-addicted mother, O'Neill was no stranger to psychological problems.

In this dramatic venture, he failed. The play was stilted, the setting forced. The protagonist is a war hero, Arnold, who believes his heroic actions have been misunderstood and that he is unworthy of the respect and honor given to him. Disgusted by the carnage he has seen and his own feelings of guilt, he is anxious and distressed. His doctor can only advise the hero “to try and forget those unavoidable horrors.” When the doctor can produce evidence of Arnold's true heroism, his symptoms of distress and anxiety instantly disappear. The play was never performed and remained unpublished in O'Neill's lifetime.