Jens Dahle and James Eberhart are both prisoners in Confederate prison at Salisbury, North Carolina. James writes in his diary:
“January 1st 1865 136 day–
Oh for a happ. New Year. Can this be one for us. God forbid. This a cold Raw day & the boys are a going fast on acc of Exposure & grub. We had a Recruiting officer at gate. Want Recruits. Nothing to eat to day. This a good day to fast on.” — James Eberhart 
Recruiters would try to convince Union soldiers to fight for the Confederacy. It is not known how many succumbed to their exhortations as the Confederates did not keep good records or their records were destroyed. Andersonville Prison is an exception. What records do exist are mostly from diarists recording what they observe. Sargent John Ely, 115th Ohio Volunteer infantry and newly arrived at Andersonville, noted in his diary that 200 of the Union prisoners volunteered for the Confederacy on that day. Later in the month, another prisoner recorded that 125 enlisted. Confederate records at Andersonville seem to corroborate such numbers. 
This practice was not limited to the South; the North conscripted Confederate prisoners as well. The officers of the Union Army sent the “Galvanized Yankees” to the west to fight the Indian Wars. Check out this article for more information: Galvanized Yankees – Meet the Confederate POWs that joined the Union Army.
Intellectually, one can understand why men would switch sides as the conditions worsened in the camps, but the prisoners who did not defect viewed the “galvanized soldiers” with “hatred and condemnation.” If you have an ancestor who fought in the war on either side but disappeared after the war, it is possible that he defected to the other side and then could not go home again. From the recruiter’s perspective, you have to wonder whether the new recruits could ever be trusted.
Photos of galvanized soldiers are not readily found. See above.  I do not know if Albert was a galvanized soldier or just very committed to the Southern cause; he certainly underwent some hardship to sign up.
Consistently, whenever the recruiting officer came to Salisbury Prison no food was offered that day.
 Florence C. McLaughlin, editor, “Diary of Salisbury Prison by James Eberhart,” The Western Pennsylvania Historical Magazine, July 1973.
 Paul Springer, Transforming Civil War Prisons: Lincoln, Lieber, and the Politics of Captivity, (New York: Routledge, 2015) 58-63. Book was found on Google books. Here is link to the source for the above: Transforming Civil War Prisons. I wish this book would have been out when I was writing my paper. It is a wonderful book and recommended reading.
 Adalbert Volk, artist, “Albert S. Johnston crossing the dessert [sic] to join the Southern army.” Library of Congress (http://www.loc.gov : accessed 30 November 2014).
Another resource is the Library of Congress Prologue article, “Trading Grey for Blue.”
The National Park Service covers the topic: