After going back and forth on the matter, Druse ultimately decides that he must kill the Confederate horseman (his father) in order to protect his fellow Union soldiers from attack. Bierce captures Druse’s sense of clarity using imagery, as seen in the following passage:
He was calm now. His teeth were firmly but not rigidly closed; his nerves were as tranquil as a sleeping babe’s — not a tremor affected any muscle of his body; his breathing, until suspended in the act of taking aim, was regular and slow. Duty had conquered; the spirit had said to the body: “Peace, be still.” He fired.
Bierce uses imagery here in order to help readers feel Druse’s sense of calm alongside him, by focusing on the sensations in his body, like how “his teeth were firmly but not rigidly closed,” “his nerves were as tranquil as a sleeping babe’s,” he no longer had any tremors, and his breathing was “regular and slow.” Rather than just telling readers that Druse felt calmer after deciding to kill the horseman, Bierce includes these details in order to help them understand on a deeper, more visceral level.
It is notable that Druse’s body starts to calm down as soon as he remembers that he has a “duty” to fulfill. While he could have prioritized a duty to his family—and not killed his father—Druse decides to prioritize his moral duty by helping the Union defeat the Confederacy. A commitment to a progressive future for the country is ultimately more important to him than saving his father’s life.