Rock Island Dungeon
“When we arrived [as Confederate prisoners] at Rock Island, early in December 1863, Col. Rust was in command with a detachment of the Fourth Invalid Corps. He was a kind-hearted old fellow and just to the prisoners; but unfortunately for us the old Colonel was soon removed, and in his place came as inhuman a brute as ever disgraced the uniform of any country, one A.J. Johnson, with his regiment of Negroes for guard duty, leaving the Fourth Invalid men…for light fatigue duty.
Men were brutally punished upon the slightest pretext. I saw prisoners tied up to the fence by their thumbs, their toes barely touching the ground in the hot, broiling sun until they would faint, and when cut down by the guards, fall limp and unconscious. While none of us dared approach for they were next to the fence, over the dead line and grinning Negro sentinels stood just above them with ready guns in hand. 
[O]ur rations had been gradually reduced to less than half the amount issued to us when we first reached the Rock Island prison. Hunger began to develop the savage instincts that lie dormant in us all; men grew ugly in temper, quarrels and fights were frequent over their scanty rations, yet this was but a foretaste of what was to come.
In the summer of 1864…we were informed that the United States government had opened a recruiting office in our prison and that all who would take the oath and join the United States army would be moved into the new pen—calf pen, we called it—furnished good clothing, bountiful rations, paid $100. bounty, the post sutler permitted to bring in whatever they wanted to eat, and that they would not be sent South to fight, but on the frontier to hold the Indians in subjection.
Never, since the Son of Man was tempted by the devil was dishonor more cunningly devised or temptingly displayed. Quite a number jumped at the bait, mostly men who were willing to take the oath under any circumstance; but after this came the heroic struggle between patriotism and starvation…But every few days starvation would claim a victory. It was pitiful. Gaunt forms with the glare of wolfish hunger in their eyes, the very pictures of famine could be seen going up to take the oath, tears streaming down their faces and curses on the Yankees from their lips, their poor, shriveled flesh showing beneath fluttering rags…”
(Forty Hours In A Dungeon At Rock Island,” B.M. Hord, Nashville, TN.  Confederate Veteran Magazine, August 1904, page 385)