Your John W. Davis probably served in the Union, not Confederate forces. Tennessee was mostly Union. There is a John W. Davis in Company E, Sixth Regiment Tnnessee Infantry. As to the PO of Pleasant, Tennesse. Back in the days of the Civil War when soldiers enlisted they did not give the town, but rather the post Office of their community. Many of these small communitues lost that identification after the war. You might call the county library of the county he enlisted from, and they could tell you if this community existed.