How did grants decision to end prisoner exchanges affect the men at Andersonville ? Why would a blockade affect civilians and prisoners ? pls hurry

In May of 1863, the Confederate Congress passed a joint resolution that formalized Davis' proclamation that black soldiers taken prisoner would not be exchanged.It was overcrowded to four times its capacity, with an inadequate water supply, inadequate food and unsanitary conditions. Of the approximately 45,000 Union prisoners held at Camp Sumter during the war, nearly 13,000 died.Many of the prisoners who claimed to have escaped from Andersonville often either escaped from other camps or in transit between camps.Captain Henry WirzBecause of public outrage and indignation in the North over conditions at Andersonville, Captain Henry Wirz was found guilty of war crimes and was hanged on November 10, 1865. It has been said that Wirz was the last casualty of Andersonville.