Fortress Britain could have been the name given to Britain in 1940 after the success of Blitzkrieg in Western Europe. Fortress Britain had to be created after the evacuation of troops at Dunkirk. There was a real fear that Britain would be attacked. The result of this was a government policy that was to turn Britain into a fortress.
The Defence of Britain Project has identified 20,000 military sites across Britain linked to World War Two. The War Office correctly guessed that the Germans would attempt a landing in the south and south-east of England. However, major diversionary raids elsewhere could not be ruled out and, as a result, near enough the whole of Britain was fortified.
General (later Field Marshal) 'Tiny' Ironside was put in charge of UK's defence. Ironside's first policy was to create a 'Coastal Crust' around the south and south-east coastlines initially, and then moving up the eastern coastline before returning to other areas. Ironside wanted a 400 mile defence around the south, south-east and eastern coastlines. This made it much larger than the Maginot Line and represented a massive building project.
Beaches were to be made impenetrable. Scaffolding was erected on most beaches so that landing craft could not land on a beach. Behind the scaffolding were placed thousands of mines. Behind the mines was barbed wire and behind the wire were more land mines. Finally, yet still on the beach, were anti-tank blocks - 13 ton concrete blocks designed to impede the movement of the tanks used in Blitzkrieg. Behind the beach area, pill boxes were built to house machine guns and to create a killing field. 18,000 pill boxes were built in the summer of 1940 alone - at the height of building, a pill box was built every 20 minutes.
Inland, and the next part of Britain's defence were 'stop lines'. Each 'stop line' defended a specific area of land and contained inland pill boxes, tank traps, barbed wire etc. Over 100 'stop lines' were built and the biggest was GHQ 'stop line' that ran the length of Britain. Each 'stop line' was manned by the Home Guard.
In the spring of 1941, the government introduced its next stage in the defence of the UK. If the 'Coastal Crust' and the 'stop lines' were broken through, each town and village had to create their own killing zones. These too would be manned by the Home Guard as it was believed that the Home Guard, being locals, would fight for their own locality with vigour.
Airfields were seen as an Achilles Heel in Britain. Though they were used for planes during the Battle of Britain, Bomber Command or by Coastal Command, they were also zones where the Germans could land planes - as the runways already existed. As a result pill boxes were built to cover each air base and decoy airbases were built to fool the Germans. This task was given to Colonel John Turner and he used set designers from Shepparton studios to assist him. They formed the top secret 'Col. Turner's Department'. They built 500 decoy air bases complete with fake runways and fake fighter planes. Some of the 'airbases' were deliberately set on fire at night to lure German bombers away from their actual targets. It is estimated that 50% of German night time attacks on air bases actually hit decoy bases.
All the above was done to ensure that if 'Operation Sealion' was ever launched it would fail. As Hitler's planned for invasion never took place, it will never be known if the work done by Ironside and others will ever have been sufficient.