My great x 3 uncle, Leonard Spears was in the 12th when it was captured at Vicksburg. He was in the 20th (Infantry) for approxiamately four months before going to the 12th. Eight months after the surrender at Vicksburg he joined Monroes Cavalry where his two other brothers, Robert and Greenberry Spears were serving. I sure would like to find out what happened in that eight month interval between surrendering and joining Monroe's unit. There was an even exchange program of prisoners (Union for Confederate, Confederate for Union)and I was wondering if it had taken that long for him to rejoin his comrades in arms. I know the siege of Vicksburg like the back of my hand, but no records of the prisoner exchanges and dates. Any help?