Postern

A postern is a secondary door or gate in a fortification or city wall. Unlike the main gate, a postern is typically smaller, less conspicuous, and placed on the side or rear of a wall or fortress. Its function is to provide restricted access for retreat, covert movement, or a quick sortie without exposing the principal entrance.

Historically, posterns were common in medieval castles, town walls, and other fortified works. They could lead to a protected passage, an inner courtyard, or a rear approach to the keep. Access was usually controlled by a separate wicket or gate and sometimes by a covered way or sally port. In many fortifications the postern allowed guards to move between enclosures while remaining comparatively hidden from besiegers at the main gate.

Architecturally, posterns are typically smaller and more discreet than primary gates. They are often integrated with defensive features such as a barbican, a ditch, or a guard chamber, and may include a secondary door or lattice gate. Some posterns opened into moats or toward inner corridors, enabling defenders to conduct operations with reduced exposure.

Etymology and usage: The term derives from Old French posterne, meaning a rear or back door, with roots in Latin indicating placement behind. In historical and architectural contexts, postern denotes a secondary entrance rather than a principal gateway. In modern narration of historical sites, the term is used to describe these discreet access points; in contemporary buildings, the equivalent might simply be called a side or service entrance.