The Redoubt was built between 1808 and 1810 to protect the port of Harwich against the threat of Napoleonic invasion. It was part of the scheme that included the construction of 29 Martello Towers on the East Anglian coast. The Redoubt is of circular shape, approximately 200 ft in diameter, with a central parade ground of 85 ft diameter. Hoists were used to lift shells from the lower level to the gun emplacements. It is similar in design to earlier redoubts at Dymchurch and Eastbourne.