At the beginning of the fighting, in 1861, no one anticipated that more than 400,000 men would become prisoners of war and that at least half of these would spend extended time in sites of what we would now call mass incarceration. The odds of being captured by the enemy in World War II were 1 in 100. In the Civil War, they were 1 in 5. As Brundage observes, three times as many Union soldiers died at the Confederate camp in Andersonville, Georgia, as at Gettysburg. Overall, approximately 10 percent of the war’s deaths occurred in prisons.