redoubt

A redoubt is a small, detached fortification used to strengthen a defensive position. The term derives from the French redoute, meaning a fortification designed to provide shelter and to deliver fire upon approaches. In English military usage from the 17th century onward, a redoubt is typically a freestanding work that guards a particular sector or objective within a larger line of defense.

Redoubts are usually built with earthen ramparts and a ditch, sometimes revetted with masonry or timber. They are often polygonal or square in plan and are designed to offer a firing step and parapet for troops and to resist assault. The usual layout may include a single gate, a covered way or ditch to approach, and positions for artillery or firearms to cover adjacent terrain.

Historically, redoubts appeared in early modern fortifications and siege warfare across Europe and the colonial world. They served to protect a flank, bolster batteries, support an enclosing fortification, or act as a reserve position. They were common in field works during the 17th to 19th centuries and were adapted to various combat requirements.

With advances in artillery in the 19th century, the term gradually gave way to broader categories such as fortlets, outworks, and glacis-based defenses. The concept persists in archaeology and historical writing as a way to describe smaller, subordinate fortifications within larger fortification systems.

Different fortification traditions used different shapes, including square, polygonal, and irregular forms, and sometimes redoubts formed part of ring fortifications or siege lines. The word is also used in place names and in the names of preserved or reconstructed sites.