Exact information concerning a nation's offensive and defensive capabilities is known only to a limited number of persons, both civilian and military, within a country. Details and aggregate statistics, military weapon technology and military planning are all classified according to a hierarchical system of increasing degrees of required secrecy. Thus the public and its elected representatives have no knowledge of military matters other than what they are told by their government. Ignorance of military affairs prevents the public from voicing approval or disapproval. Under the cloak of military secrecy: imprisonment of political 'criminals' may be conducted; operations may be undertaken against labour or civil unrest; and inhumane warfare and war crimes engaged upon.
In the USA, there was great secrecy concerning the Vietnamese War, the Bay of Pigs landing in Cuba, and the abortive rescue mission in Iran.
National defence depends on military secrecy. The vital nature of military information is indicated by frequent espionage activities reported in the press. However, military secrecy can be self-defeating by, for example, delaying the flow of information and decisions needed for defence.