The Battle Royale Program was a Japanese military research experiment implemented after World War II in which classes of high school students were taken to isolated locations and forced to fight to the death until only one remained alive. To ensure compliance, an explosive metal collar was attached to the necks of every student. It also recorded each student's vital signs, location, and conversation. Officially it was used for military experiments, but in reality the Program was used to instil terror in the population to prevent a rebellion.