Top Secret (TS) is the highest level of classified information. Prior to 1942, the United Kingdom and other members of the British Empire used Most Secret, but this was later changed to match the United States' category name of Top Secret in order to simplify Allied interoperability. The unauthorized disclosure of Top Secret information is expected to cause harm and be of grave threat to national security.

Secret

Secret material is often regarded as causative of "serious damage" to

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