Postal censorship is the inspection or examination of mail, most often by governments, that can include opening, reading or marking of covers, postcards, parcels or other postal packets. Postal censorship primarily takes place during war time or periods of unrest, though occasionally during other times, like; periods of civil disorder or a state of emergency, as was the case in Ireland during 1939-1945. Both covert and overt postal censorship have taken place. The study of postal censorship is a philatelic topic of postal history.