Since the question has been answered, I have a follow up question. Upon the surrender of Ft. Donelson, perhaps 10,000 or more soldiers were sent to POW camps. Many of them had their one year enlistments extended while they were dying or struggeling to exist in places like Camp Douglas.

When the prisoners at Camp Douglas (for example) were exchanged, was there any difference in their status as an enlisted soldier from men who had not been to prison? Were they also required to complete "3 years or duration of the War"? If so, do you have any records that indicate how many of them decided to just go home after literally being sold up the river by incompetents like Generals Floyd and Pillow?