AP English Literature help

SO, basically, I have two days to write five essays on Ambrose Bierce. I chose the works "Chickamauga", "The Horseman in the Sky", and "The Occurrence at Owl Creek Bridge". Right now I am working on one that is going to be comparing the Setting of "Chickamauga" and "The Horseman in the Sky" and I am haveing trouble getting started. I suppose and help on how they may be similar and different will help. I am looking for thoughts that maybe I have not picked up on, so anything will be helpful. Thanks for any help you may give.