Discuss why you believe Peyton Farquhar undertakes his efforts to destroy Owl Creek Bridge in the first place.

It seems that Peyton Farquhar attempts to destroy the Owl Creek Bridge because he believes that its destruction would injure the Union war effort and aid the Confederacy. As a slave owner, "he was naturally an original secessionist and ardently devoted to the Southern cause." He didn't want to join the army, likely due to his "imperious nature"—in other words, he doesn't like to take orders—but he is interested in finding an "opportunity for distinction:" some way in which he can help the South to defeat the Union Army and retain its so-called way of life. He feels himself to be, at heart, a soldier, and he likewise believes that "all is fair in love and war."
When the apparently Confederate soldier tells him that injuring the rail lines would very seriously hinder the Union Army's progress in the South, Farquhar seems to decide to attempt to burn the bridge, as the soldier suggests is possible due to a large quantity of wood that has accumulated near it. However, because the soldier is really a Federal scout in Confederate garb, Farquhar's attack is expected, and so he is caught and executed for his crime. He is willing to risk his personal safety in order to help the South, and he does not seem to regret his decision.