The Immortal Six Hundred were 600 Confederate officers that were held prisoner by the Union Army in 1864-65. They were intentionally starved and 46 died as a result. They are known as the "Immortal Six Hundred" because they refused to take an oath of allegiance to the U.S. under duress.
In June 1864, the Confederate Army imprisoned five generals and forty-five Union Army officers in the city of Charleston, South Carolina, using them as human shields in an attempt to stop Union artillery from firing on the city. In retaliation, United States Secretary of War Edwin M. Stanton ordered fifty captured Confederate officers, of similar ranks, to be taken to Morris Island, South Carolina, at the entrance to Charleston Harbor. The Confederates were landed on Morris Island late in July of that year.
The Confederate had originally contended that Charleston should not be shelled. The correspondence between Major General John G. Foster, commanding the Federal Department of the South, and Major General Samuel Jones, commanding the Confederate Department of South Carolina, Georgia, and Florida, indicates the Confederates subsequently accepted the military nature of Charleston as a target. Soon the correspondence turned to an exchange of these high-ranking prisoners.
Instructions from the War Department reached Foster in late July, and he coordinated an exchange of the fifty prisoners on July 29. Exchange of the fifty officers actually took place on August 4, 1864. However, at that time Jones brought 600 additional prisoners to Charleston, in part to press for a larger prisoner exchange. In retaliation for the treatment of Federal prisoners, Foster asked for a like number of Confederate prisoners to be placed on Morris Island. These men became known in the South as the Immortal Six Hundred.
At one point General Foster planned an exchange of the six hundred, but General Ulysses S. Grant, who had previously terminated all prisoner of war exchanges due to the history of Confederate mistreatment of captured US African-American troops, wrote, "In no circumstances will he be allowed to make exchanges of prisoners of war ."