A large part of the 34th Mississippi Infantry was captured on the 24th of November, 1863 at the Battle of Lookout Mountain, Tennessee. Most, if not all, of the enlisted men were taken to Rock Island, Illinois prison. Some of these men were recruited into the Union Army to fight Indians in the west. They became known as "Galvanized Yankees." They were the 3rd regiment U.S. volunteers.
The following is an excerpt from the James D. Rowland biography:
"President Lincoln, under great political pressure to lighten the draft quotas on the states, sent a trusted young Army aide, Captain Henry R. Rathbone, to Rock Island Barracks to form three regiments of "Volunteer Infantry" from among the Confederate prisoners. This was all done behind general Grant’s back, as the general absolutely did not approve of the plan to enlist the Confederate prisoners. Captain Rathbone enlisted James D. Rowland as a Private in the 3rd U.S. Volunteer Infantry Regiment on 18 October 1864 for a one year term James was subsequently assigned to Company G. Incidentally, the aforementioned Captain Rathbone was President Lincoln’s bodyguard at Ford Theater on the night of his assassination."
The 'Galvanized Yankees,' as they came to be known, went into Federal service on the condition that they would not be required to fight against the Confederacy. Instead, they were sent west to keep the mail routes and roads open and safe from raiding Indians. Still, many Confederates considered these men to be traitors. In addition to their freedom, the volunteers received a $100 bounty along with food, clothing and medical care."
An excellent use of military resources, another little known way that your male ancestors from the South ended up in the West.