The Device Forts, also known as Henrician castles and blockhouses, were a series of artillery fortifications built to defend the coast of England and Wales by Henry VIII.^{[2][lower-alpha 1]} They ranged from large stone castles, to small blockhouses and earthwork bulwarks.^[4] Armed with artillery, the forts were intended to be used against enemy ships before they could land forces or attack vessels lying in harbour.^[5] The castles were commanded by captains appointed by the Crown, overseeing small garrisons of professional gunners and soldiers, who would be supplemented by local militia in an emergency.^[6] The Device programme was hugely expensive, costing a total of £376,000, much of it raised from the proceeds of the Dissolution of the Monasteries.^{[7][lower-alpha 2]}

Henrician castles Henrician blockhouses and bulwarks^[1]

The fate of the Device Forts over the coming years varied.^[9] Some of the defences were left to deteriorate and were decommissioned only a few years after their construction.^[10] Others were kept in service and used during the English Civil War, the Anglo-Dutch Wars, the Napoleonic Wars and, upgraded with more modern artillery and defences, throughout the 19th century.^[11] By 1900, however, developments in guns and armour had made most of the Device Forts that remained in service simply too small to be practical in modern coastal defence.^[12] Despite being brought back into use during the Second World War, by the 1950s those fortifications still in use were considered redundant and finally decommissioned.^[13] Coastal erosion over the centuries had extensively damaged or completely destroyed some sites, but others have been restored and opened to the public as tourist attractions.^[14]