The Redoubt was built between 1804 and 1810 to support the associated Martello towers in defending against the threat of an invasion by Napoleon. It has defended the Eastbourne coast for nearly 200 years. Like its twin Dymchurch Redoubt it was built as a barracks and supply depot for the towers, and designed for 11 guns, although only 10 guns were installed. During the First World War the Redoubt was used by the military police as a headquarters and temporary jail. Following this, the Redoubt was purchased by Eastbourne Borough Council for £150 with the plan to turn it into a venue for leisure activities. During the Second World War the building was requisitioned by the army to be used for storage. Canadian troops also spent time there in the build up to the D-Day landings. After the war, the Redoubt was home to a model village (miniature park) and an aquarium. The model village was vandalised in the 1970s, and the aquarium closed in 1996.
The redoubt opened as a military museum in 1977, and is now the largest military museum in south east England. It contains military collections of The Royal Sussex Regiment who moved to the museum in 1983, The Queen's Royal Irish Hussars (see also The Queen's Royal Hussars), who moved in 1988 and the founding collection, the Sussex Combined Services. In addition the museum also features displays on the History of the British Army, the Life of the Redoubt display and a model of the Redoubt Fortress.
The museum is open to the public from 29th March 2013 through to 17th November 2013. The museum is open 7 days a week, 10am – 5pm. The winter months are used for building restoration and the creation of new displays.