internment, in international law, detention of the nationals or property of an enemy or a belligerent. A belligerent will intern enemy merchant ships or take them as prize, and a neutral should intern both belligerent ships that fail to leave its ports within a specified time and belligerent troops that enter its territory. The practice of detaining persons considered dangerous during a war is often called internment, even though they may not be enemy nationals. In World War II the United States detained persons of Japanese ancestry and German or Italian citizenship in relocation centers on the mainland; Japanese and Japanese Americans were also detained in internment camps in Hawaii. The Geneva Convention of 1949 on the Protection of Civilian Persons in Time of War provides for the unrestricted departure of enemy aliens from the territory of a belligerent at the outbreak of conflict, and the humane treatment of those aliens who choose to remain.