Isolation for the purpose of abuse

Isolation is often used to get more power over a person. This power is then used for abuse. Isolating the victim from the outside world is important to get psychological control over the victim. Isolation reduces the opportunity of the victim to be rescued. It will also make the victim more dependent on the abuser.
This includes controlling a persons social activity: the people they see, the people they talk to, and the places they visit. Sometimes it also includes controlling the material they read. It can also include wanting to know where the victim is. Very often, a victim has to get permission to get medical treatment.
Isolation is often combined with other forms of abuse:
Cults often use these techniques.