Prisoners of war captured by UN forces in Korean were first taken to Pusan; from there they were ferried across the sea to Koje-Do Island. Here, in the shadow of the hills that dominated the island, were thirty-seven vast, adjoining, wired compounds. In the spring of 1952, the Communists began infiltrating men who deliberately allowed themselves to be taken prisoner, with orders to seize internal control of the POW compounds. This they were able to do without the slightest difficulty. A storm broke upon Koje-Do, of a kind never witnessed before in any military prison camp in history. But there had been incidents as early as the summer of 1951, in which guards and prisoners were killed.
Koje-Do quickly became, as the Communists intended, a second front in the Korean War. Their purpose was to achieve a major propaganda victory -- to project the United Nations as the brutal persecutors and murderers of their prisoners.
Max Hastings included an excellent section on Koje-Do in his book The Korean War. Here are some links to more articles and websites:
Koje-Do: Truce Tent and Fighting Front
War Behind The Wire: Koje-do Prison Camp