Shortly after the fall of Ft. Donelson, the C.S.A. conscripted all the one year volunteer enlistments to "three years or the end of the War". I have often wondered how demoralizing that was to the 8 or 10 thousand rebel POW's who must have felt they had been sold out by Generals Floyd and Pillow. Some of them, perhaps many, deserted during the fall and early winter of 1862 upon being exchanged.
The Confederacy obviously had a shortage of every kind of resource, including men and that meant longer enlistments and more hardships than endured by most Union troops. My father was a combat veteran and when I told him about the military records that showed one of my ancestors had deserted he told me not to judge him. That was good advice.