An interesting narrative technique Ambrose Bierce uses in "An Occurrence at Owl Creek Bridge" is the flashback presented in Part II. Part I describes the setting and the preparation of the hanging, and Part III resumes with the hanging scene, bringing it to completion, ending with the main character swinging "from side to side beneath the timbers of the Owl Creek bridge."
Part II gives us the background of Peyton Farquhar, the main character, the man who is being hanged. We find out that his life up until now has unfolded this way:
1. Farquhar, a slave owner, advocates for secession along with other plantation owners.
2. When the war breaks out, Farquhar does not enlist in the Confederate Army, but wishes he could support the cause in a tangible way.
3. Farquhar performs various unnamed tasks on behalf of the Confederacy.
4. Farquhar is sitting on his porch when a gray-clad, presumably Confederate soldier rides up and hints that if someone wanted to burn the Owl Creek bridge to prevent the Union Army's advance, it could be easily accomplished.
5. Farquhar then plots to burn the bridge and acts on the soldier's suggestion, possibly "get[ting] the better of the sentinel," or trying to, and attempting to burn the bridge. However, he is captured by the Union Army because the soldier he had talked to had actually been a "Federal scout," and Farquhar had been caught in a sting operation.
The actual action taken by Farquhar that led to his capture by the Union Army is implied rather than explicitly stated in Part II. It may be that Farquhar planned to hang the sentinel from the bridge because Farquhar says to the scout, "Suppose a man—a civilian and a student of hanging—should elude the picket post and perhaps get the better of the sentinel?" Farquhar is obviously referring to himself. Thus the Union Army's decision to hang him from the bridge is an ironically appropriate way to carry out his execution.