Anti-War
The clearest and most overarching theme delineated through the text is that of opposition to war. The author uses irony and paradox to present both the fantasy-world glory of mythic warriors and the ugly, muddy, blood reality of war. What is presented as a game for immature minds becomes in the hands of immature leadership a game played on a far more massive scale where everybody winds up a loser in some sense and where winning is boiled down to merely surviving to see another day.
The Incoherence of War
Part of that overarching indictment of war is a more specific and focused theme about war is an incoherent activity. When seen from one perspective, that which is worth dying for may seem like nothing weightier than a silly pantomime. The emotional attachment to a cause on one side lose all its coherent stability and collapse into support for inhumanity on the other side. The battle of Chickamauga plays out with absolutely no difference for both the adult narrator and the child playing on the spot, but there is absolutely no cohesion between the two conflicting perspectives looking at the exact same scene from two utterly disconnected vantage points.
PTSD
Of course, Ambrose Bierce did not really set out to write a story about post-traumatic stress disorder since it did not exist as a diagnosis but only as a misunderstood condition. Even so, the story's publication more than three decades after the Battle of Chickamauga and its thematic focus on the inability both to understand and to communicate the horrors of warfare speak to the delay that often occurs between the events a soldier experiences and the time in which he is finally able to articulate himself. A delay exists between when the child sees what is going on around him and when he finally is able to understand it.
Likewise, the soldier with the missing jaw does understand what is going on, but is physical incapable of expressing whatever message it is that vainly struggles to communicate to the boy. Very important in this dichotomy is that even if the soldier could have successfully articulated himself, the little boy would still not have been able to understand because of his deafness. So the story speaks not only to the soldiers suffering PTSD who cannot verbalize to their satisfaction the fullness of their experiences, but it also suggests that part of the problem with communication is on the side of the listener (or reader, to take the theme to its logical conclusion) who even if they can hear it may still not be able to fully understand it.
