A small, and usually a roughly constructed, fort or outwork of varying shape, commonly erected for a temporary purpose, and without flanking defenses, -- used esp. in fortifying tops of hills and passes, and positions in hostile territory.

In permanent works, an outwork placed within another outwork. See F and i in Illust. of Ravelin.

1) A small separate defensive work (blockhouse or earthen works); 2) Detached outworks as part of a larger defensive plan, usually square without defensive flanks. Could also be polygonal or hexegonal shapes.

Isolated military construction and autonomous

A central tower within a fortification atop which artillery can be mounted.

a small defensive earthwork fortification, sometimes temporary, and sometimes used to reinforce a permanent rampart.

Detached, independent outwork.

Small self-contained fieldwork, a refuge for soldiers outside the main defenses.

A type of fort or fortification used for defense. Could be of modest size or quite substantial.

A small fort of varying shape, usually of a temporary nature.

An enclosed fortification without bastions. Fort George is a bastioned fort.

This was larger and stronger. It might be a square or some other multiangled shape, but it was always completely enclosed, never open at one end.

A small field work, usually square or polygonal in form, used as an outlying defense of a more strongly defended fortified position.

A small, roughly constructed fortification, usually temporary, often used to defend high points of land.

somewhere for soldiers to hide while they are fighting

an enclosed fortification designed to be defended from all sides.  The trace of a redoubt could be square, polygonal, or occasionally circular.  A redoubt could stand alone as a detached work, serve as a place of refuge within a larger fortification, or be incorporated into a continuous line of entrenchments as an artillery or infantry strong point.  Redoubts were a common feature of all military eras.

A redoubt is a fort or fort system usually consisting of an enclosed defensive emplacement outside a larger fort. It is meant to protect soldiers outside the main line of defense and is often hastily constructed. Redoubts were a component of the military strategies of most European empires during the colonial era, although the concept of redoubts has existed back to medieval times.