Throughout History, Dover Castle has been used as a highly fortified military garrison to protect Britain’s shores from invaders. Originally the Castle’s foundations, built by the Romans, resembled a hillfort and a lighthouse was also later erected on Castle Hill. This fort known as Dubris, was demolished in AD 215 1 and the lighthouse was reused for the construction of the church of St Mary in Castro around AD 1000. The Castle was remodelled in 1180 into the one we recognise today; the rebuilding was established by Henry II who created the most advanced castle design in Europe.2

By the 1800s, the castle had become a formidable artillery fortress and barracks. During the Georgian period when the secret war tunnels were first established, these tunnels were known as the Casemates and they served as an underground barracks for the army until the 1840’s when they were abandoned.3 Consequently the nation’s defences were in an abysmal state, and the port of Dover and its coasts were susceptible to invasion due to the weaknesses of the fortifications.

Following this crisis of the nation’s defences a series of vital improvements were made to the castle, these consisted of the structural strengthening of the inner bailey and great tower in 1853. In order to improve the weaknesses of the existing barracks a new set of buildings for the Army were established in the years 1856-1870. These included: The Officer’s New Barracks (1856), The Regimental Institute (1868) and The Garrison School (1870). 4 These new buildings and improvements to the existing infrastructure of the underground barracks and the secret network of tunnels would prove to be vital in the most important stages of the Second World War.

During the Second World War, Dover Castle played a vital role in the strategic operations of the British Army. Firstly, the Castle was home to the only underground barracks in the country as it’s secret network of seven tunnels were able to accommodate around 2,000 troops.5 In order to manage this volume of soldiers, two new levels were built, the first of these new tunnels Annexe was completed in 1942, this tunnel served as an underground military hospital. Throughout the War, several other secret tunnels including: A- Annexe, B- Bastion, C- Casemate, D- Deep Underground Military Position and E-Esplanade were extended and remodelled to serve as a secret command centre, war rooms and an underground military barracks.6

This secret network of underground tunnels were vital in the Evacuation of Dunkirk (Operation Dynamo) and in the key deception operations of the Second World War including Operation Fortitude South which was a top secret Allied deception campaign that aimed to deceive the Germans into believing that the invasion in Europe would take place in Calais.7

In order to accomplish this, large volumes of coded fake messages to trick the Germans were passed throughout the county and British and Canadian units worked around the clock in the secret tunnels beneath Dover Castle to simulate the communications of the fictional army known as The First United States Army Group.8 Dover itself played a vital part in Fortitude as large numbers of dummy tanks and vehicles were deployed on Dover’s coasts and harbours to create the impression that FUSAG was preparing for the invasion of Calais. Ultimately, the D-Day Deception campaign (Operation Fortitude) based in Kent was successful in deceiving the Germans into believing that the Allied invasion of Europe would take place in Calais, the actual real invasion was in Normandy and the deception saved thousands of Allied lives and marked a major turning point in the war for the Allies.


  1. English Heritage (2010) Dover Castle

  2. English Heritage (2010) Dover Castle

  3. Historic England (1999) Dover Castle

  4. Historic England (1999) Dover Castle

  5. BBC/Discover Kent (2014) Secret Tunnels of Dover Castle

  6. (2021) Military Tunnels in the White Cliffs of Dover

  7. English Heritage (2010) D-Day Deception: Operation Fortitude South, Dover Castle

  8. English Heritage (2010) D-Day Deception: Operation Fortitude South, Dover Castle