It is one of the most impressive of the Device Forts being built by Henry VIII between 1539 and 1540 as an artillery fortress to counter the threat of invasion from Catholic France and Spain. It is shaped like a Tudor rose, being perfectly symmetrical, with a low, circular keep at its centre. Around the circumference of the keep are six bastions, with a further series of six bastions in the curtain wall, one of which serves as the gatehouse. All the outer walls of the castle and bastions are rounded to both provide strength and to deflect shot more efficiently than flat walls. Over 200 cannon and gun ports were set within the walls and the entire structure was completely surrounded by a very deep, wide moat.
In 1648, during the Civil War, Deal Castle was besieged but after that it never engaged in any further military action. Fortified during the Napoleonic Wars, many alterations were made during the 18th and 19th centuries. The Governor's lodgings were rebuilt at the beginning of the 19th century, only to be destroyed again in 1941 by German bombs in the Second World War. It was the official residence of the Captain of the Cinque Ports, until 1951 and is now owned by English Heritage.