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. Traditionally, the Crown had left coastal defences in the hands of local lords and communities but the threat of French and Spanish invasion led the King to issue an order, called a "device", for a major programme of work between 1539 and 1547. The fortifications ranged from large stone castles positioned to protect the Downs anchorage in Kent, to small blockhouses overlooking the entrance to Milford Haven in Pembrokeshire, and earthwork bulwarks along the Essex coast. Some forts operated independently, others were designed to be mutually reinforcing. The Device programme was hugely expensive, costing a total of £376,000 ; much of this was raised from the proceeds of the Dissolution of the Monasteries a few years before.
16th-century keep and gun platform at Pendennis Castle
Reconstruction of life amongst the 16th-century garrison at St Mawes Castle
Reconstruction of a 16th-century cannon and gun crew at Pendennis Castle
Little Dennis Blockhouse in 2008
A blockhouse is a small fortification, usually consisting of one or more rooms with loopholes, allowing its defenders to fire in various directions. It is usually an isolated fort in the form of a single building, serving as a defensive strong point against any enemy that does not possess siege equipment or, in modern times, artillery, air force or cruise missiles. A fortification intended to resist these weapons is more likely to qualify as a fortress or a redoubt, or in modern times, be an underground bunker. However, a blockhouse may also refer to a room within a larger fortification, usually a battery or redoubt.
Completed in 1750, Fort Edward in Nova Scotia, Canada is the oldest remaining military blockhouse in North America.
Reconstructed European wooden keep at Saint-Sylvain-d'Anjou, France, has a strong resemblance to a North American western frontier log blockhouse
The Henrican blockhouse at Mount Edgcumbe near Plymouth, Devon, which is believed to date from circa 1545
Blockhouse of Westreme Battery, built in 1715–16 in Mellieħa, Malta