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A postern is a secondary door or gate in a fortification such as a city wall or castle curtain wall. Posterns were often located in a concealed location which allowed the occupants to come and go inconspicuously. In the event of a siege, a postern could act as a sally port, allowing defenders to make a sortie on the besiegers. Placed in a less exposed, less visible location, they were usually relatively small, and therefore easily defensible.[1]
Posterns were one of the essential means of ensuring safe communication between the enceinte and the outerworks of a defensive fortification.[2] An 1850 West Point course summary on permanent fortifications discusses the placement and construction of posterns.[3]
In literature, a postern features in the Le Chanson de Girart de Roussillon, where the hero makes use of one to escape when betrayed; as does Renaud de Montauban in the chanson de geste, The Four Sons of Aymon. A postern also provided a safe retreat for Ogier the Dane.[1]
In Malory's Le Morte d'Arthur, "La Cote de Male Tayle" is rescued at the Castle Orgulous when a damsel slips through the postern to find his horse and ties it to the postern so that La Cote de Male Tayle can escape the 100 knights assailing him.[15]
The term is occasionally used in other contexts referring to a secondary door placed after a main entrance.