In "An Occurrence at Owl Creek Bridge," what point is Bierce making about military formalities?
In this story set during the Civil War, there is one reference made to "military etiquette," which I assume is the focus of your question. It comes in the first section as the soldiers prepare formally for the hanging of Peyton Farquhar:
Death is a dignitary who when he comes announced is to be received with formal manifestations of respect, even by those most familiar with him. In the code of military etiquette, silence and fixity are forms of deference.
Aspects to note about this quote are the formality of the author's style. Bierce's formal diction and his personification of death as a "dignitary" evoke a solemn mood that befits a hanging. Note how the soldiers present are described as standing in "parade rest" position, looking at what is going on "stonily" and without movement. This effect is highlighted when Bierce describes the onlookers as "sentinels," who could have been "statues" because they moved so little. All this serves to reinforce the formality of this hanging, making it a sombre event.