Galvanized Yankees was a term from the American Civil War denoting former Confederate prisoners of war who swore allegiance to the United States and joined the Union Army. Approximately 5,600 former Confederate soldiers enlisted in the "United States Volunteers", organized into six regiments of infantry between January 1864 and November 1866. Of those, more than 250 had begun their service as Union soldiers, were captured in battle, then enlisted in prison to join a regiment of the Confederate States Army. They surrendered to Union forces in December 1864 and were held by the United States as deserters, but were saved from prosecution by being enlisted in the 5th and 6th U.S. Volunteers. An additional 800 former Confederates served in volunteer regiments raised by the states, forming ten companies. Four of those companies saw combat in the Western Theater against the Confederate Army, two served on the western frontier, and one became an independent company of U.S. Volunteers, serving in Minnesota.