A redoubt 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 line of defense and can be a permanent structure or a hastily-constructed temporary fortification. 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 defense of static positions and siege warfare, though combat bases and fire bases of the Vietnam War, and Forward Operating Bases of the Iraq War and Afghanistan can be seen as the descendants of this type of fortified position.
See the Battle of Poltava (1709), the Battle of Yorktown (1781), the Battle of Bunker Hill (1775), the Lines of Torres Vedras of the Peninsular War (1809–1810), the Battle of Borodino (1812), the Charge of the Light Brigade (1854), the Railroad Redoubt of the Battle of Vicksburg (1863), and the Hawthorn Ridge Redoubt of World War I (1916) for examples where redoubts played a crucial role in military history.