An illustration of Devonshire Redoubt, Bermuda, 1614
A redoubt (historically redout) is a fort or fort system usually consisting of an enclosed defensive emplacement outside a larger fort, usually relying on earthworks, though others are constructed of stone or brick. It is meant to protect soldiers outside the main defensive line and can be a permanent structure or a hastily-constructed temporary fortification. The word means "a place of retreat". Redoubts were a component of the military strategies of most European empires during the colonial era, especially in the outer works of Vauban-style fortresses made popular during the 17th century, although the concept of redoubts has existed since medieval times. A redoubt differs from a redan in that the redan is open in the rear, whereas the redoubt was considered an enclosed work.
The advent of mobile warfare in the 20th century generally diminished the importance of the defence of static positions and siege warfare.
During the Wars of the Three Kingdoms redoubts were frequently built to protect older fortifications from the more effective artillery of the period. Often close to ancient fortifications there were small hills that overlooked the defences, but in previous centuries these had been too far from the fortifications to be a threat. A small hill close to Worcester was used as an artillery platform by the Parliamentarians when they successfully besieged Worcester in 1646. In 1651 before the Battle of Worcester the hill was turned into a redoubt by the Royalists, (the remains of which can be seen today in Fort Royal Hill Park). During the Battle of Worcester, the Parliamentarians captured this redoubt and turned its guns on Worcester. In so doing they made the defence of the city untenable. This action effectively ended the battle, the last of the English Civil War.
A national redoubt is an area to which the remnant forces of a nation can be withdrawn if the main battle has been lost, or beforehand if defeat is considered inevitable. Typically a region is chosen with a geography favoring defense, such as a mountainous area or a peninsula, in order to function as a final hold-out to preserve national independence for the duration of the conflict.