Allusion in The Killer Angels helps to enhance the theme of the novel in three ways. (1) Allusion precipitates events or circumstances that reveal motivation in characters, thus furthering their development in keeping with the depiction of the theme. (2) It provides a vehicle to expose the inner thoughts and feelings of characters and even groups of characters, thus exposing the deeper meaning of the theme. (3) It ties in with ironic metaphors to further the importance of the thematic points (e.g., duality of humankind).
A brief example of a literary allusion is the reference to Hamlet in which Chamberlain recites a speech from comparing man to angels. This is where Chamberlain father then replies that if the comparison on the speech is true, then men are "killing angels." Chamberlain's character is developed through this because he goes on to give a speech called "Man the Killer Angel," thus providing understanding of thematic elements. A brief example of a musical allusion is the way Armistead's song moved the whole camp and provided a vehicle for author Michael Shaara to explore the thoughts and feelings of a great number of characters, thereby exposing the deeper meaning and ramification of a thematic point. These allusions tie in with ironic metaphors that paint the imagery, the pictures, relevant to the significance of the theme, thus further exposing the importance of the thematic points.