Who is telling the story in Hemingway's "Soldier's Home"?What impact does this have on the story? Is this first person narration, third person...

The story is told from the point of view of an unnamed, third person, omniscient narrator.  From his vantage point the narrator can recount the sequence of events in the story, give insight into how the characters react and what they are thinking and feeling, and digress to provide background and supplementary information.  This allows the reader to see the whole picture and enables him to develop an understanding of multiple aspects of the story simultaneously.