Company "I" of the 25th Alabama Regiment was recruited in Calhoun County, which bordered Georgia in that day and time. The 25th Alabama would have fought in those battles. The question is, do the two service files for this man match the information you posted here? Parker could have seen fighting at Chickamauga only as a member of the 25th Alabama, since the 53rd Georgia arrived a day or so too late for the battle. Of course the Georgia regiment wouldn't have been involved in the battles around Atlanta. Besides, Parker had already gone to lovely Elmira in upstate New York by that time, there to enjoy a long, all-expense paid vacation courtesy of the Federal government.