Sally port

A sally port is a secure, controlled entryway to a fortification or prison. The entrance is usually protected by some means, such as a fixed wall on the outside, parallel to the door—which must be circumvented to enter and prevents direct enemy fire from a distance. It may include two sets of doors that can be barred independently to further delay enemy penetration.

From around 1600 to 1900, a sally port was a sort of dock where boats picked up or dropped off ship crews from vessels anchored offshore. That meaning occasionally still occurs, especially in coastal Great Britain.

Etymology and historical usage

The word port is ultimately from Latin porta for door. Often the term postern is used synonymously. It can also mean an underground tunnel, or passage (i.e., a secret exit for those besieged).

A sally, ultimately derived from Latin salīre (to jump), or sortie, is a military maneuver, typically during a siege, made by a defending force to harass isolated or vulnerable attackers before retreating to their defenses. Sallies are a common way for besieged forces to reduce the strength and preparedness of a besieging army; a sally port is therefore essentially a door in a castle or city wall, that allows troops to make sallies without compromising the defensive strength of fortifications.