Hello
The war had negative effects on everyone, including authors. For example, when the war was over, writers, in their majority, began to put their war violent experience into writing, as a way to get those feelings off their cheast; therefore, the style, form, and the thematic of the discourse in American literature would be changed. In addition, the American Civil war affected the people in psicological terms, becuase they started questioning their morality and reality; they started having a different vision of the world.
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