Who is(are) the antagonist(s)?
The antagonists are the Union forces that tricked Peyton into trying to blow up the bridge. Through flashback, Bierce writes about an incident that occurred a few days before the story opens. A man wearing a confederate uniform asked for some water. He also tells Peyton and his wife that the Owl Creek Bridge is not well guarded. The man was actually a Union spy and he misleads Peyton into thinking he can easily blow up the bridge. Of course, he has been captured when the story opens and the Union spy's trap was successful. The Union army will finish what the spy began, the entrapment of Peyton.