 This movie is based on actual events. After North Korean commandos  tried to assassinate South Korean President Park Chung Hee in 1972,  the Southern Government set up a unit to kill North Korean President  Kim Il Sung. The unit was made up of prisoners sentenced to death  for various offenses. During their preparation, the South Koreans  scrapped the idea and allegedly were going to kill the prisoners to  keep the whole thing a secret. The prisoners got wind of this and  revolted.