I have looked into the meridian campaign and as you noted the first was not apart of that campaign. He notes in his letters the 117th Illinois, has the wife direct letters to the 117th. Which was part of the Meridian Campaign. I looked into it thinking maybe he enlisted or became the unit sutler but came to a dead end. Seems he was only with the unit for a month or two. so i doubt he enlisted. my guess is he lied to his wife, and went off as you noted to make a buck or two anyway he could.