On January 31, 1968, 31 North Korean commandos infiltrated South Korea in an attempted assassination of President Park Chung-hee. In retaliation, the South Korean military assembled a team of 31 criminals on the island of Silmido to kill Kim Il-sung in a suicide mission to redeem their honor, but the mission was canceled, leaving them disappointed. It is loosely based on a 1970s military uprising.